I’ve upgraded this server to PHP 5.2.0 [1] using the Debian Backports [2] repository, please post a comment or email me (send it to chris at this domain) if you spot any problems!
First impressions are very good, I’ve not been bitten by these WordPress problems [3] (yet) and memory usage seems a hell of a lot better than 5.1. The only wrinkle is that I had to increase memory_limit to 128M to get posting articles to work, but whereas before that would have killed the system completely it seems OK for now..