For AIM accounts -- pop.aim.com doesn't exist, but if you use pop.aol.com it works.
There are no advantages and only disadvantages to accessing Aim\Aol via POP3 in PP, but it can be beneficial to access via POP3 in your client, depending on your needs.
wow... 2gb pop+imap access?? that's actually pretty good news if you want to use the imap technique to transfer old emails into your gmail account. too bad i've done it already - this would've been sooooo much easier.