I've used IE8 since the beta last year. This site was definately giving me difficulty pre-RTM but it seems to finally be working properly with the newest version.
Frankly though, this site has given me problems with IE regardless of the version since the latest revision about a year or so ago--IE6, IE7, IE8--they all seemed to crash after clicking the "next" buttons in the longer articles more than four or five pages into it. This is regardless of what PC I use--home built, Dell, HP--also happened on 2000, XP, or Vista. Being the only site that has given me so many issues on IE, it kind of pissed me off a bit. Still, I haven't had the problem with the final release of IE8.
As far as gmail goes, it's kind of a mixed thing. Most of the time, it works just fine, but on occassion, the navigation menus for the email screws up. I have no idea why it would work most of the time and not all of the time.
Other than gmail and a certain fan-based Star Wars web site, I have not had any issues with the final release of IE8.