The current version should work with the PHP 4.0.3-dev tree. It's only when we make an API change in Zend that the Optimizer actually changes.
hm, I remember having tried a few times and got some errors an windows, now I don´t get any errors (all scripts seem to work too) but I also don´t get any hint (using phpinfo()) that I´m using the optimizer
IIRC there was some info in the "This program makes use of the Zend scripting language engine:" field, now there isn´t any, neither on windows nor on linux...
If that message has been removed I assume the optimizer has been loaded and works without problems
andré