Importing WAV vs AIFF & song info

AIFF is the format that your CDs come in. If you import in the same file format then theoretically you should lose little in the transfer and have the best quality. Converting from one format to another will most likely affect quality to some degree. One downside of importing in AIFF of course is the size of the files, pretty soon you will take up a considerable amount of disc space. For that reason most people use a compressed format such as AAC (MP4) or MP3 and accept the quality drop. An alternative is Apple Lossless which is a high quality encoder which will reduce the file size to a little over half that of AIFF.

The information isn't determined by the import format, it's done by the iTunes software. It wouldn't matter if you imported as AIFF, AAC, MP3 or WAV. This document covers how iTunes stores the information: http://docs.info.apple.com/article.html?artnum=93952

I'm by no means an expert but here's my interpretation of how iTunes works according to the link above. When you import a track into iTunes, it either collects song info from an on line database or you put it in manually. This goes into an info file within iTunes. iTunes saves this information into the "CD Info.cidb" file and the information is associated with the various audio files. Basically it's a reference table if you like. If you then take the song to another PC all it has is an audio file and a file name as the references are held in the original iTunes folder. Thus one iTunes "remembers" the information and the other has no data to reference.

WAV format does not include ID3 tags to store artist, album, track, album art, etc.

More info than you probably want: http://en.wikipedia.org/wiki/ID3

It's a personal preference which format you use. I like to use my songs on another device than iPod, so I rip MP3s.