I hear playstation2 is a headache and the xbox is rather good, what about the cube?
Devkit is the machine you run the complied programs on. Comes with an accompanying SDK, and I'm pretty sure you've gotta supply your own IDE to work with. Devkits usually come in several flavours - for PS2, there's a TEST, which looks physically alot like a normal PS2 (I haven't played with those too much - I think the main diff is that they can use burned CD/DVDs for testing), and a TOOL, which is basically a normal computer that communicates with an internal PS2 (TOOL's are you're main debugging machine); XBox's have green Debug machines and White SDK's (the white ones are the ?ber machines, I've only played around with a debug kit); and I've got next to no idea about GCNs, the one's I've seen are big blue boxes.
Gamecube probbably comes in a little better than PS2, but nowhere near as good as Xbox.