@Andrew: I tested with zzjazz.sty: whether I have the Audible Lead-in box checked in Preferences or not I always have the count-in. I tested from scratch after starting BIB. Have you tried on your side with the Mac version (latest update)?
Yes I have. When you say you always have the count-in, is it just the beginning 2 measures you are talking about, or do you hear the clicks? If you want to remove the beginning 2 measures you'll need to also uncheck "Allow lead-in bars", which is in the same Preferences dialog. Note that the song may not start right away if it needs to be generated. But with zzjazz (no RealTracks) it will start pretty much right away...