Big things on my wish list:
-User selectable HTML or ASCI e-mail alert/subscription options with ASCI as the default. I tend to like to include lots of tags in some of my posts as the forum manager and they make the e-mail's look awful. Thanks to Garrit for the tag stripping hack.
-Easier to edit e-mail confirmation messages for newly registered members. Perhaps make the form fields like the random password, username, forum name, etc. markup tags on a simple form page where you could create the e-mail. While it might seem minor, that first message you get from a community you sign up for is critical and often has some bearing on whether the person ever comes back and participates. The more it can be customized, the better.
-Better help documentation. The current FAQ is not enough for forum novices. Eileen's context help hack is a great step in the right direction, but it needs to get updated for the new version and kept up to date as new features are added.
-More control over the 'user list' feature -- like being able to pick which fields are included. ICQ is not a big thing for my forum, but listing of location or company is... having more control over that would beat the heck out of trying to modify the perl on my own.. If anybody knows a good hack, let me know.
-Integration of the 'attachment icon' hack that Eileen came up with. Several of my users have not noticed that anything is attached to a post in the current approach.
Templates and site integration sound nice, but I'd take the above tweaks first.
And thanks for asking!!