LimeWire doesn't read mp3 tags (yet?). However, some software (I believe BearShare does this) can read the bitrate of the mp3 so you know what quality of mp3 you are downloading.

Yes - People see the exact string you see in your library window, not what you see in the Finder or Windows Explorer (aka My Computer).

You can edit filenames from the Library. Selecting a file and the clicking on it again lets you change the name. Use the CTRL+C and CTRL+V command to copy and paste phrases. I usually name my files this way:

ARTIST - SONG.mp3
Delirious - Deeper.mp3

:-)