I just tried to compile PHP 4.3.3RC3 with mySQL4 4.0.13 as an external library. It started with lots and lots of errors because PHP was still trying to use the mysql.so extension. I then removed that extension from my php.ini and now everything seems to be running just fine.

I also noticed that PHP 4.3.2 is FINALLY in debian unstable, but it’s much more fun to compile stuff on your own ;)

I would also like to note that 4.3.3 is noticably faster than 4.3.2, mainly because of a filesystem change in how PHP handles files (So I’ve been told)
Once it goes stable/released, I recommend you all upgrade :)