Feature:
It didn't come with a sustain pedal like the Fatar SL-161 did, but overall this thing beats the Fatar SL-161 hands down. Make sure to order a seperate sustain pedal for the Radium. The assignable knobs and sliders are impressive, this opens up new possibilities during performance and recording.

Quality:
Very good quality, light yet sturdy controller. The 8 sliders are plastic and slide somewhat smoothly, and the 8 knobs are rubber and feel fine during the full range of travel. There is no center stop on the knobs, but that is ok because center position on the knob might not correspond to center on the software anyhow (but there may be a way to make that happen).

Value:
This is definitely worth the price, it is $10 cheaper than the Fatar SL-161 and a far better quality item with more features.

Desirability:
It looks really good. It is more compact than the Fatar, lighter, and still sturdy plastic. It is light grey and looks just fine.

Sound:
When hooked to Propellerhead's Reason and a hi-fi system, it has to sound good.

Support:
I dont know about m-audio support, but I do know that zZounds has done a great job replacing a defective set of Fatar Studiologic SL-161 keyboards (yes I tried 2 of them) with this thing which has way more options and is overall a better quality keyboard. My props to the zZounds customer support and returns department.

Overall:
On its own this keyboard does the job and then some. In comparison to the Fatar Studiologic SL-161, the M-audio Radium absolutely rules. Just dont forget to pick up a nice sustain pedal (should run approx $28 from zZounds)

Feature:
More features than I personally wanted. I'm not the kind of person that needs every control bound to a slider, I'm capable of changing the bindings when I wanna control something else, all it takes is two clicks. So this worked out just fine. I do wish the keyboard was a full piano size. that's 88 keys, right? I would buy a Radium88. - The Hamster Alliance

Quality:
It's a little slow. the readout is delayed and jumpier than the Oxygen 8. On the Oxy8, when you twist a knob the numbers look like they're doing exactly what you're doing. on the Radium they don't happen as fast.

Value:
It's worth what you pay for, which isn't very much. Not a bad keyboard. Would be cool though if it had servo controlled sliders...but that's a-whole-nother price range. :P

Desirability:
This keyboard weights absolutely nothing, that's a good keypoint about it. Very sleek and thin design. Grey matches anything. doesn't have the company plastered all over it like big keyboard manufacturers label their keyboards.

Overall:
I plan on having this keyboard a long time. I'm not a big spender, I like to keep my cash and only buy necessities. so Until they update MIDI itself - I'm not updating my midi controller. I don't use it much. not because it's bad, but just because I have limited use for it - I program most my music by manually punching in values anyways. I just use it to plunk a few notes or chords and see if they work before putting them down - or add some human variation into a sound. I chose this one because it was cheap.