A straightforward, no-nonsense, USB controller, which seems to suit me well for home recording duties. It's a bit plasticky, but it's fine - and good at the price.
Although the Key Rig software supplied on CD is for Windows, there is an Intel Mac version available for free online (search for M-Audio Key Rig Software Mac), which was easy enough to install - the drawbar organ's pretty good, pianos are fine, and the synth's alright too. Will run standalone or as VST plugins with your DAW of choice.
Ableton Live Lite 6 came with it too.