Odd issue that came up, in that the blog went down due to part of a header file disappearing. Easy enough to fix, and I took the opportunity to update to the newer version while I had the hood open anyway. Thanks to Jim for PM’ing me that the page was not loading.
The install files are more than clear on this point, but to mention again an important part of the upgrade process for WordPress is to disable all plugins before you upgrade. I think that is what might have been giving the upgrade flow issues when I tried previously, or maybe I was just lucky today.
Anyway, technical issue fixed, new blog engine installed, all good.