i've just setup a clean ubercart alpha7b install (at http://ubercart.anarres.ca), and successfully upgraded it to your attached alpha7c release candidate, and had no troubles whatsoever.
i also reviewed the install/upgrade docs, and everything seems to be fairly accurate. one thing i couldn't find that i'm pretty sure was on the site pre-crash, is a doc describing the key blocks to setup, and how to configure them initially (ie. so the cart/catalog blocks don't show up on admin pages, etc).
anyway, i'm also working on a soon-to-be-launched (sandbox copy of a) production site upgrade, and my initial impression is that all's well. unfortunately i'm running outta steam for tonight, so i'm going to drop it and wait for the official alpha7c release in the morning.
the interesting part of the live site upgrade is that we're using a slightly modified version of the contributed ratequote shipping module, which implements the checkout_pane hook. i'll post a fresh tarball to that page when i get it working for alpha7c tomorrow