I went on another synth binge recently and decided to check out some of the more prominent synths available for OS X, whether I had triend them before or not.
I don't think it's worthwhile to go into long, detailed, fluffy tirades like you'll find on most review sites; this aims to be more pragmatic, if self-serving.
Albino 3 [***+]
(Note, I used Albino 2 quite a bit, before my whole studio was stolen.) I still really like this synth; I can move around in it very quickly, I like the sound, it's got some good filter flexibility, and the "digital" oscs make some beautiful wavetabley sounds that you can "tone down" ("warm up"?) by setting one side to digital and the other to a typical VA waeform and going 80% toward the VA side: this is the "zone" I really like sounds to be in, and I don't have other synths that can get to that place this easily.
That said, I own Predator and, despite the less flexible OSCs / Filters there, the overall sound of Predator serves me well enough, and I don't think shelling out $250 for something that ultimately sounds so similar is worthwhile.
It's a great synth, and one of the first that I would recommend to others. But for my situation, I'll pass. Again. ...but I admit, some part of me really misses this and wants it back.
Alchemy [**]
I must admit, I was really hot to trot in trying out this synth. I really loved White Noise's Additive Synth, back in the day, for the ability to 'draw' sounds, and Alchemy (properly) mixes in VA to make things cleaner. It sounded good in the video demos. And it has the coolest name for a VST I've seen yet. ...but I grabbed the demo, I gave it its due, and I deleted it. It was too complex. It lacks that magic ingredient of "character"... or, if it had it, I didn't like it. Pass.
Battery [**+]
Kinda hard to argue why I need this, given that I have Stylus RMX, but I find that RMX lacks some... oh... I dunno, maybe it's just the workflow--I'd like to be able to apply effects to individual drum parts instead of having to process entire sets... I find it more restrictive; just not what I was used to with tracking drums (which is what I am most comfortable with). I'm also just getting more interested in percussion, and Battery brings some of that back, rather than having to rely on loops. ...There's nothing about Battery that I particularly liked, though... it's just a different tool for drums, and one I don't have. I may pass on it and just stick with RMX and add a simpler drum synth like MicroTonic. I haven't made up my mind. That said, it's currently half-off the price. THAT said, it might be half-off because they are about to come out with a better alternative, or discontinue it. Soooooo...
Blue [***+]
I've tried Blue a few times in the past, and have always come away with the same impression: it's nice, but not something I need. It's mostly about the FM synthesis, which I tend not to like (but read the FM8 review, below), which may be part of the problem. But I also own Predator, so I have a lot of those "Rob Papen" sounds already, and don't feel I need more. It's also a little greedy in terms of CPU.
Fab Filter Twin [****]
What a fantastic synth! A tiny little interface (probably a bit too small for my tastes) which just feels nice to work in (nice animations, good colors, clear workflow): all to the good. But the filters! They are the second best filter I've heard in software (the best being impOscar's dirty little bastard), and as a result, this synth strikes me as a "must have", and very much worth the $170 price tag. I've heard others compare its sound to a Virus, which I don't think is fair (having owned a Virus): the filter is nice, but not that nice. This strikes me as a bit more like a Nord: cleaner, with some oompf. It's now on my shopping list. Did I say "fantastic" yet? It's fantastic!
FM8 [****]
Okay, if you've talked to me about synths, then you know I have a deep-set hatred for FM synthesis, in general. But I looked at this again with a completely open mind, and found that... yeah, I hate most FM sounds. But others--pads and bells and some "fake" analog styles--can sound wonderful, and have a level of expression that isn't easy in the world of VA. Again, it's that balance of VA warmth and power with digital details. In the end, I found myself really liking FM8, if only for the presets (I couldn't program FM to save my life).
Massive [*****]
I passed on Massive the last time I used it. It is billed as this great big, fat, tower-of-sound with no equal, and I was completely underwhelmed with it, excepting a few kick-ass bass sounds that my music is too wimpy to handle anyway. I didn't bother digging into the interface much, because it's unclear and makes very poor use of space. I totally misunderstood Massive. I approached it this week with an open mind, however, and found it is not some VA-killer... it's a wavetable synth with an amazing ability to scan its tables and come up with some digital brilliance. Who knew? To my mind, this is absolutely the best wavetable synth one can afford, Microwaves notwithstanding. Absolutely a must-own synth, especially for me. It's capable of exactly the kinds of sounds I want in my music: digital details with analog power. I can't believe I've overlooked this for so long.
Must. Have. ...It's just a question of which to get first, this or Surge. ...And, yeah, they are similar in capabilities, but I think both are worth owning. ...particularly for the style of music I am attempting to capture.
MicroTonic [***+]
A drum synth. I miss my drum synths! I did Gewesen with drum synths (free ones, at that!), and I loved the sound of the percussion on that album. I want it back. Microtonic seems to deliver, and in a slick package with low CPU use. I need a little more time with it to see if it could work within my workflow... that damn nag message keeps me from using it any more than for a few minutes of checking out the sounds (which are very nice).
Minimonsta [****]
I really like this synth. It's smooth, it's powerful, it's versitile, and unless you go nuts, it's reasonable on CPU-usage. But as I continued to play with it, I couldn't help but think that this is the perfect synth for Boards of Canada, and less the kind of synth that I personally want to use. It's a great VSTi, sounds great, and if money weren't so tight, this would be a quick purchase for me. But it's got to be lower-priority, at least for now.
Moog Modular V [***]
I really thought I was going to fall in love with this synth. ...But after using it for a few hours, I realized that A) I just wouldn't use it that often, for the style I write, and B) it really didn't sound as big and warm as I thought, especially compared to Minimonsta. ...or really, anything, run through a good compressor with a little saturation. Plus, I'm just not a hardware modular guy, so I find the interface tedious and the CPU overhead obnoxious.
Omnisphere [****]
Okay, so there is no demo of this that one can download and try... I only mention it because I watched a few more videos (aside from the official ones), and it does seem like it's worth the price to upgrade Atmosphere (which I own) to this guy. ...When I have the money. : ) It intimidates me, though. Atmosphere is already big... this is ginormous.
Surge [*****]
Yeah, this synth has been on my shopping list for over a year now (hey, I'm poor), but I gave it another spin, and feel just as psyched about it now as I did then. See the review of Massive, above, for exactly why: it's a wavetable/VA hybrid, with some real punch and nice details. I like the interface of Surge, too... it's very different, but the way they handle the mod matrix works really well for me (though I do wish a few more were hardwired). I find I can tweak patches with almost the same ease as Albino and Predator. A great synth... a real classic, and it appears to have been overlooked by the masses... which is just another reason I must own it in my book (I love those synths on the fringe).
...And Others...
I considered some other synths, but didn't grab the demos for various reasons. Arturia's stuff, for example: I'd just rather have tomorrow's classics than yesterday's. Xphrase came to mind, but it's really all about the arp, and I don't use arps. Ever. I thought about Kontakt and Reaktor, but those just seem to be deeper than I want to go.