This keyboard is, in my humble opinion, the best in its price range. I have tried the most famous ones like the Akai, some M-Audio ones and the Nektar Impact lineup, but this is by far the best.
The layout is absolutely gorgeous, which may not be needed to make music, but I personally think it is important that your gear is beautiful, and I find this keyboard quite aesthetically pleasing.
For Ableton users this is a no-brainer, since the amount of features you get to handle the software are absolutely insane. Despite that, Novation have taken other DAW users into consideration and brought up some nice features and add-ons for non Ableton users.
Technically speaking, I am no expert, but I find the keybed much more confortable to play than the other ones and the pots are nice. They wobble a bit but can't ask much.
I find the slider-type modulation and pitch wheels much more comfortable to use than the real thing. Also, they show no bump since they are flat with the surface, so I think it is a great design decision.
The pads are no special good in quality concerns (also not special bad, either, they work absolutely fine), but the device comes with a piece of sofware (Components) that lets you program every single pad and pot in every possible way, which I find absolutely amazing.
Speaking of software, at the beginning, they let you download everything that you get from the device from a nice landing page, so it is very easy to get everything set up.
All in all, I think you don't give up in anything with this device, while still keeping it cheap. Can't imagine how good their higher end devices may be.