After having been stuck on version 2.0.1 for over two years, I’ve just upgraded to the most recent version, 2.5.1. The only hiccup was needing to ask my web provider to give me a new MySQL database: since 2.5, Wordpress has required MySQL 4.0 or newer.
Otherwise, it all seems to be running very smoothly. Do let me know if you see anything crazy. I hope to upgrade more frequently in future, as it was a far better experience than I’d expected.