G-Mail has a couple of POP idiosyncracies, just to be aware of:
1) AFAIK, it isn't really possible to set G-Mail to use multiple client programs like Mail on two Macs or Mail on a Mac and Outlook on a PC. Whatever you set it to do, it still will only download a new message to the first computer that asks for it, and pretend like it's already been read for all the others. Even though this is not supposed to be what it does. Also it will ignore your deletion of e-mails from the client program, and keep them unless you delete them from the web interface (which I guess is not so bad, since the mailbox is so big, but I do have thousands of MacRumors forum update messages....
)
2) On the good side, you can still send messages to people from the webmail interface without mucking anything up. When you do, you'll get the SENT mail in your INBOX, oddly enough, in Mail. I have a Mail Rule set up to just move it to go with other sent messages (I keep an offline archive of sent messages, so I actually put it there, rather than in Sent Mail).... In the end, this works fairly nicely, although Mail may not be able to relate the two messages, so you may not be able to click on the arrow by the original message to see the reply you made, if you made it from webmail.
Other than that, G-Mail and Mail.app have done me great.
