I'm now using Zend Server CE as my Drupal development environment on Windows. Previously, I used the WAMP package and was very satisfied with it due to its flexibility and stability. However, I noticed that recent projects began to get slower and slower. They had many modules enabled so by the completion time, they began to feel like real CPU eating monsters.
(Details: I have a Core 2 Duo 3GHz with 4GB RAM – should be more than enough for a Drupal site, even a heavy one. PHP opcaches didn't help much.)
It was time to try something new – Zend Server Community Edition http://www.zend.com/en/products/server-ce/ – the platform from the mother of PHP…
Amazing! The project's home page (development, so caching off) load time was reduced from 12 seconds (WAMP) to less than 3 seconds (Zend Sever)!
I would agree that the php.ini setting can make a difference, but not 4 times… What really does the trick are two Zend Server components – Zend Data Cache and Zend Optimizer+. It's also running PHP in Fast CGI mode, which is not a trivial task to set-up with bare bone Apache and PHP on Windows.
Give it a try, see the difference and let us know what you think. Best of all, it's free! ;)