Concept 2 is a great synth. The first one was decent enough, but quite expensive in a crowded market. Version 2 builds on the inherent strengths of the original Concept with a new granular oscillator, backed up with really good content. It comes with loads of presets and has to be one of the easiest synths you will ever use.
The brilliance of Concept lies in its unique take on modulation. Instead of cramming the GUI with 5 envelopes and 5 LFOs and 5 MSEGs, Concept has 5 modulation sources that can be any of these. Each is colour coded and you can see at a glance where modulation has been applied. Clicking in the coloured window expands it to reveal controls and a modulation list. I think it is just about as close to perfect as it gets and it makes the GUI so much less cluttered, which leads to the best results in the least time.
As well as the new granular osc, the original V/A style osc is still available and it's actually pretty good. Each osc has two waveforms you can mix together and there are FM ratio and depth controls. The Granular osc takes things to another level. As I said, there is lots of good sample content to throw into it and there are three panels of controls to play around with, including more FM. I don't find it as easy to get good results from as Pigments but you can do plenty with it. The content covers a lot of territory, from a range of sampled synths through to cockatoo and parrot sounds.
The filter doesn't try to model any classic analogue sound, it's a very straight interpretation of what a resonant filter should be. But it is definitely quite useful, with LP, HP and BP modes at 12 or 24dB/octave, as well as a formant mode. There is a pre-filter drive to fatten up the sound, too.
There are 3 effects slots and a choice of 10 different effects. They all do a pretty good job and the reverb is a convolution jobbie and you can drag'n'drop any sample file into it for some pretty interesting/weird effects. The filter effect is exactly the same as the synth filter and all the effects parameters can be modulated, so there is a lot of sound shaping power here.
Overall, this is a terrific synth that is really easy to get great results from with a minimum of effort. The presets are great and plentiful and even after a few weeks I haven't gone through them all because I keep getting distracted by great patches. CPU usage isn't too bad and the resizable GUI is mostly great, although some switches are a bit small. If you're looking at Pigments, you should also check this out. It's not as full featured but I reckon it covers a lot of sonic territory and I think it sounds better.