John Lim looks at the release of PHP 5.1 with a bit more skeptical eye in his latest blog post today.

Well PHP 5.1.0 is out. This is a monumental piece of work, and congratulations to the PHP 5 internals team for all the hard work. However it feels rushed through the door. Apparently there are compatibility problems (with typecasting when parameter passing, the prototype date class, and possibly other stuff.) Wait for the patches.

He also mentions some of the turmoil that's been going on on the PHP internals mailing list lately, especially pre-5.1 release...