The topic tagging box has been changed to separate tag adding and deleting and the interface for tagging topics has been overhauled. There are still some messaging bugs and various tweaks needed but this should make it much easier to delete or change your tags.
All the main old urls for forums, topics and posts have now been redirected to the new urls to preserve your links and bookmarks from the old software.
You can now choose between a serif and sans-serif font for posts in addtion to choosing a larger font size on your preference page. Nick's idea of making users enter their age and just using that as a font size has been put on indefinite hold.
There is now a preference to turn off avatars, or to choose between small or large sized avatars. This should make some of the more vocal "large avatar" advocates happy (I won't mention any names so that joefromchicago doesn't feel bad).
The ability to search tags has been added to the tag listings (what were the old tag clouds) and it will search as you type to allow you to find any existing tag you can spell (and with the as-you-type searching even some you don't).
The topic and post ratings will be changing in the future, but to help eliminate the focus on the negative ratings the display has had a floor set at 0, effectively making 0 the minimum rating currently displayed for a post or topic.
The ability to view a users' individual posts has been placed on the user profile page. This allows you to easily see a user's most recent individual posts while the "My Posts" page shows the topics they have posted in and can be sorted by recent activity by any of the participants.
At launch the "My Posts" page displayed indivdidual user posts, which made it hard to follow the topics members participated in by the recent topic activity. The page has now been changed to show topics the user has posted in instead of individual posts.
Now all offsite links open in a new window like the old site software used to do. Additionally all offsite links use "nofollow" to indicate to search engines to ignore them. This should provide less motivation for people to spam the site for the purpose of manipulating search rankings.