I ripped to AIFF for a long time and recently ran out of space. I converted it all to ALAC and freed up a ton of space. If I had space, I'd use AIFF for pure archival purposes.
Can't tell a difference, but the piece of mind is there with AIFF.
One thing I love about using iTunes (and there aren't many) is that you don't need to keep copies of your stuff in MP3 or AAC. You can tell iTunes to downconvert to AAC when transferring to your device. All ALAC in the library and it goes down to 256 AAC when I put it on my phone or iPod.