Characteristics that motivated my choice was the eight assignable knobs and nine assignable sliders, also I did enjoy the direct link mode.
It has a midi connection that works really great with Pro Tools and other daw's also a sustain pedal input.
The general configuration of the program it's very simple, yet very very fast.
The manual has a nice description regarding the knobs, slides, velocity sensitive keys, and also about the unique Select buttons for on-the-fly step-through of presets, program changes and MIDI channels.
The patch selection is easy to follow even for an amateur, it's very straight-forward and sensitive.
What I like most about are the 49 velocity-sensitive keys , I also enjoy 8 MIDI-assignable knobs
9 MIDI-assignable sliders, 6 dedicated transport controls, dedicated track up/down buttons, and many other cool features, like DirectLink and full compatibility with Windows XP, Windows Vista
and Mac OS X.
The prices is just around 150 $ , check on amazon, I really think you couldn't find something better for this price, and generally you can do some great things with a small controller like Oxygen 49.
I do enjoy how the keys feel, however it's not the greatest velocity sensitive keyboard out there, but it works pretty decent for it's money, quality of sound is on a high level and I like the material of the midi.
I tried several models, some more expensive, some less, however M-audio made me a fan, I really think they create a nice balance between price and quality.
Keys are quick, velocity sensitive, the controllers work great, it's bad it doesn't have some drums features, however if you're looking something for your own studio, this is your best choice for a small amount of money.
I would buy this product again and again, even just for fun, and it works pretty good if you're on the road a lot, check it out.