We just launched our Ubercart store! http://uzumaki.com.au
This was my first shot at using both Drupal and Ubercart, and we're very happy with the result.
It's Drupal 6 and Ubercart 6.x-2.4. We used the Acquia Prosper theme for it's base, which really helped me to understand the theming and templating side of things, expecially for the Ubercart specific stuff.
One great thing about using Drupal/Ubercart was the ability to rapidly try new things during development. It's so easy to move everything around and add new blocks.
My favourite part though, is how easy it was to setup navigation of products using facets. This is one area I feel other car parts stores are lacking, it can be quite clunky to find the right part.
It's a very simple implementation of Ubercart, but we like it that way!
Let me know what you think, or shoot us an email on our contact page.
A big thanks for all the hard work!