I dont think so. I set them, then do a rebuild right after. I'm not actively changing Exclude or Prioirties other then befor a rebuild that I do manually or when I do testing (uninstall reinstall) on the other oses. Its just been with my xp, I use both windows 7 beta and Vista with the same programs. Usally when I change the Exclude, i'm on another os that has the same Exclude list like my xp. Only real differents is xp is 32 bit and the others are 64 bit.
Even if so, I check the file cache and it isnt filled with music or image files that I excluded. Mainly the system, dll, TTF, exe, LNK, VDF, XML, and some other little files are in there only. After it does that werid rebuild randomly it goes back to <10% with only a few files (random files from the old list). The USB usally goes down a little too or stays the same.