If you use evox or nexgen, both are pretty much basic ftp compatible, transmit, hefty ftp, cli ftp, etc should all work fine (the do for me at least) - what's really missing is any feasable support for xdk development, which, without setting up some sort of i386-based compiler just isn't going to happen.
A day-to-day user using a mac with xbox should be prettymuch be ready-to-go however. Someone I know is workign to recompile xiso for osx to support extraction (no messy vpc anymore). but alas, without the xdk and with moderate to low usefulness of openxdk, the mac isn't going to be programming the xbox natively anytime soon.