There have been no major changes on the VBA front. The object models have been updated to reflect the new features, but the main failings of the VBA implementation remain. Debugging is still next to impossible - you don't even get the name of the procedure that causes the error, let alone the line.

I have been impressed with the implementation of smart tags in Office XP, and you will be glad to know that you can develop your own, for integration with Office XP! What's more, the SDK needed to do this is entirely free, and available from here. You should be warned, however, that you need to be extremely efficient in writing your Smart Tags, as your code will be called for every single word that is typed. Failure to do so results in the program becoming unusable!

The Developers Edition includes some extra tools such as a Code Librarian, and a number of Add-Ins, which may be worth a look. Unfortunately, the Developers Edition of Office XP was unavailable for review at the time of writing.