GD, JSON, mod_rewrite, IP address - done
I also added a check that suggests using the latest and greatest for each of Apache, PHP and MySQL.
For the email check, it seems like a good idea, but who do we send it to? The user himself? If we rely on mail()'s return value, I suspect the test won't be as reliable as it should be.
@aaron and westi: I like the idea of adding a checkbox near the run tests button, as in "send me the results by email". it's simple enough to implement, not intrusive at all, and it could be useful when delivering support.
@Idealien: there is, yes. I added a check for safe_mode and another for open_basedir. When either or both are raised, it frequently means you can't create folders.
@miqrogroove: if you've a potential patch to check for the stuff from Suhosin that causes problems, please send it by email.
re the lost terms, I think it should be fixed in WP directly. in the upgrader for instance.