I've owned this for quite some time, and it's long overdue for the review it deserves.
In short, this is some of the best money I've ever spent. I don't understand when people say that this is overpriced...thousands of sounds and over 3 gig of info and presets for roughly $360.00...fantastic!! I paid over $600 for my Roland XV-5050 which has far less waveform content, and lacks the overall quality of the sounds in Atmosphere.
It's GUI is very elegant and just looking at it tells me I'm using something cool. Some may consider it a bit large, but I think it's perfect. When I have a GUI up I want to be able to see it. You can always minimize or close the window. I think it's far more annoying to have a GUI that is too small (Imposcar for example is a little too small for me).
The sounds are really, really, REALLY, good. Although it is a rompler, you do get to adjust some basic "synth" paramaters. Also, the ability to combine sounds to make your own patches is cool. It covers Atmospheric sounds really well "duh!" but surprisingly, it's not a one trick pony. It also features quite a selection of synth sounds sampled from your favorite big name hardware synths as well. Some basses are included as well, but are the most limited of the bunch. Pads, some fantastic strings, sweeps, and drones are the main focus of this product, and I couldn't think of anything Spectrasonics missed.
The presets are fantastic, and inspiring, which is what I look for in a rompler.
Now, my only couple of quibbles are....
1) No syncable LFOs yet. This was promised, and apparently still is, but instead of with the current engine (from my understanding it came to light that they can't achieve it with the current one) it is likely we'll receive it with a most likely "paid" upgrade to a newer version/engine.
2) Loads into RAM. I know, obvious right. BUT, if you are at all lacking in RAM keep in mind some of the larger patches can EASILY consume over 100 meg of your memory, and we're not even talking multiple instances yet. I don't particularly care that it doesn't stream from disk or anything, just something one of you guys may have a problem with. On the note of multiple instances though, Atmosphere has EXTREMELY LOW cpu usage...so load them up if you've got the RAM.
Basically, if I was forced (and I mean FORCED!) to whittle down my collection of VSTs, there's no way I would even consider putting this one on the chopping block. I think that says it all.