windows apps can read aiff, it's just not as common
I'll second that. But I'm thinking that the last time I saw an AIFF "in the wild" was about a decade ago. And WinAmp (equipped with the proper codecs) would play pretty much anything you threw at it, even then. Anyway...
Craig T and Scooter have the right idea. If you're not worried about tagging the files, shuffling them around the Intarwebz, or taking up inordinate amounts of storage space, there's no reason to bother with FLAC. With hard drive prices coming down, storage really isn't even a big issue. Still; I just bought a 750GB SATA drive for $130 but I'm still going to FLAC my newer recordings for the reasons mentioned in the posts above (tagging and fingerprinting). It does make cataloguing (and checking) the files pretty easy.