I've made a couple of audio CDs using 3" discs and there are a couple of things to watch out for. Most software doesn't seem to recognize 3" discs as normal CDs, so while it will burn fine make sure you don't try to put more than 21 minutes of audio on it or the program might crap out on you.
Also, every disc I burned ended with an error. I suppose the program was trying to scan the whole radius of a normal CD and couldn't read out as far as it wanted.
I guess the last issue would be slot-loading CD players- don't use 'em. 🙂
atx