I use AIFF. Haven't spend much time comparing the different formats because I find this sort of A/B testing tedious. AIFF seems to be a nice compromise between tagging ability and lack of compression. General consensus seems to be that WAV has the potential for best fidelity while FLAC/ALAC may not sound as good. Storage is so bloody cheap why bother with compression at all? I mean, this is a site dedicated to maximum fidelity, correct? What's a few hundred bucks extra for storage capacity in the context of a most of our systems?