I'm not sure that the user docs make it very obvious what the various ubercart blocks do or how to use them. This has come up with a client who saw the catalog block on another ubercart site and wanted the same on his site, but didn't know how to make it happen. Partly it's familiarity with Drupal (a more experienced drupal admin/editor would immediately recognise that it was a block on this other site), but he's been administering blocks on his site for a few months now, he's not stupid, but it still didn't click for him. Searching through the docs revealed very little.
Perhaps it would be good to describe what the blocks do/offer in relevant sections and how to enable them (or a link to somewhere about how to enable them). I'd be happy to write something up, but not sure if or how you guys would like this information organised.
Re: Description and usage of blocks in user docs
Excellent idea. I'll leave the exact title up to you, but something in the Configuring the Store section (a child page added to http://www.ubercart.org/docs/user/297/configuring_your_store with a weight of -9) about "Drupal Block Settings" might do well. It could include a general description of what blocks are in Drupal and a summary of the blocks in Drupal core - cart, catalog, store links. There are a few tidbits about setting these up in the docs, but a central page would do better.