The major difference is the new Security Centre that monitors your virus software to makesure it is uptodate and the upgraded Firewall that is now on by default. If you install another firewall with the new code, it will handover control to it and turn itself off. It only looks after incoming traffic, so it doesnt replace any of the third party firewalls.<br /><br />IE now has a pop-up blockers, which has worked here perfectly. The rest are all the latest security releases and some that were never released till now. It has been pretty stable here since RC1 and RC2. Just don't tell Bill Gates, but I have been surprised how smooth the update was and how stable it has been.<br /><br />I hate to say it, but I have been happy with the update so far. The new security center and the pop-up improvements are worth the upgrade.