For the most part, I have used WAMP on Windows XP for development and used Simple Helix for magento hosting; they really do make Magento run fast on their server.

Recently working on a project in which the client wants to host the web site themselves, but by default, the LAMP implementation is totally not optimized for Magento.

Did some research and came across this post filled with performance tuning tips..althought i haven’t tried them, but I believe the tips are worth a try if you are hosting your own magento installation.

http://www.magentocommerce.com/boards/viewthread/36225/

blog posting magento, performance tuning