Try using HipHop before using the word "simple." Take it from me, as someone who's been playing with it inside of the last 72 hours, it's not an instant plug-in option, and it's absolutely not simple. You're compiling PHP scripts to C++, and if you use any non-standard modules, you're going to be in for some fun.

This option is simple: it's a plug-in module, just like APC, and it requires very little setup or configuration.

If you're going from using nothing to using Zend Optimizer+, you should be blown away by the difference it makes.