I've yet to post up a broad roadmap for Ubercart, but a big item on the list is to continue to make it easier for Ubercart to be themed/tweaked. Currently, our modules have hardcoded styles and an insufficient use of classes. A lot of this was due to quick coding and oversight on our part as we created the modules. Some of it was also due to ignorance and best practices. We've been working to fix this up in core, but there's just a lot we're going to miss.
So, to help the effort, I'd like this thread to become a backlog of things that need to be changed in core to solidify our styles and clean up our .css files. I'm pretty sure there are unused properties floating around in there, and I'm more sure there are things we could be doing better in the module code.
I must confess that I don't consider these changes to be important enough to hold up a 1.0 release, although others may disagree. Currently you can still override things in your themes, it's just not as easy/consistent as we'd like it to be. My goal will be for any items that show up on this backlog to be changed when we update Ubercart 1.0 for Drupal 6. We can then readdress the situation and audit the code for any further changes when work begins in earnest on Ubercart 2.0.
Thanks for all your help, and a big thanks to those who have donated time and patches in the past to bring the code to where it is now!