It was in tests for some time already, now it seems more widely available. It still has few rough edges as I have heard, not working 100% with all email software, but hopefully that will be taken care for soon. And one needs to allow for pop3 by setting it up in options first, I think that shall be default like other mailers. Anyway the 30 secs wasted with setting up are well worth it .
The reason I love gmail, is because of the way it lays out the "conversations". I wouldn't want to change to using it for pop3 because that functionality won't be there...
What I really like is the sign in and download speed compared with Hotmail's POP. Database size I guess.
I also like the conversations very much. The good thing is that it is not either conversations or pop3, you can have both (if you need to). I use gmail mostly for searching, and also for comfortable reading of conversations, whereas pop3 is good for quick access to new messages where needed.