I’ve upgraded WordPress to version 2.5, and the Barthelme theme to version 4.5 (which is only compatible with WP2.5+). Let me know if you see any problems with the site.
One problem that I had with upgrading: I use widgets in my sidebar, including three text widgets for my feed block, my Google ads, and a hidden one at the end that includes my statistics counter. After upgrading, I went into the Widgets section, set a few parameters (there are some new options, such as being allowed to set a custom title on the Search widget) and saved the changes; this caused all the text widgets to become blank. They were still there, just empty. Luckily, I had seen this when upgrading another site earlier today, and had saved the contents of the widgets to paste back in. I deleted each of the text widgets and recreated them with the saved text that I had, and they seem to work fine now when I make edits to other widgets and re-save.
I’m having a bit of a problem posting from Windows Live Writer; I reset my credentials and tried a couple of times before I could publish this post successfully. Hopefully that’s a temporary glitch.