I decided to give PHP 5.0.1 a try, so now my home server (this server) is running PHP 5.0.1.
You might notice Serendipity has ZERO problems with PHP5 :) So far I have not, to my supprise, encountered any problems with PHP5 at all. The trick is now to code stuff so it’s still compatable with PHP4, which might be harder than you imagine.

On a somewhat related note, I am now mentioned in the PHP credits / phpcredits() … “User Note Maintainers Mehdi Achour, Friedhelm Betz, Vincent Gevers, Aidan Lister, Nuno Lopes, Tom Sommer“, and also in the documentation :)