I bought my XBOX used (so as not to directly support M$) about a year ago, and put a MOD chip and 120GB Hard Drive in it right away and have not had any regrets since.
I was looking at those plans for that port adaptor for the XBOX Joypad, and unfortunatly it looks like it is only designed to support 1 button, but it is so simple, I don't understand why all the buttons could not be made to work. As for me, I am quite happy using the XBOX control pad over an old Amiga joypad.
I have stayed up all night messing with the latest release of this emu, and I have to say it is a nice update since version 0.7. The speed is still your basic 020 speed, it still does not seem to support Picasso96, JIT, or any of the fancy things that WinUAE has, but it is catching up slowly but surely! People in the forums claim to have gotten OS 3.9 running on it, slowly, but running none the less, but for me it would boot, but not load the icons. :/
I did set up OS 3.1 and that ran good, pretty much like a stock Amiga 1200. I installed MCP, Visual Prefs, Class Act, Magic Menu, Happy Env, King Con, and a few other tweaks and everyting is running pretty well, though I wish he would just add in USB mouse support instead of forcing us to use the Joypad for that too. On the good side of things, the Keyboard does work fine.
Every Hard Drive game I installed ran PERFECTLY, Demos run great, Floppy Games run great, everything is awsome, just can't wait for some updates like I was saying, cause Genetic Species and Gloom DX would be very welcome. What would be really kool is if they added in drivers or something for the XBOX's ethernet port....
Anyhow, please visit dude man's page and sign up for the forums there. We already have a few "real" Amiga users, but we could always use more.