Current PHP is 5.4. Did you perform any test or benchmark with the new version? Do you gain anything from it? By the way, your project looks very interesting!
Very limited tests, one PECL extension for my projects was updated to support 5.4 only recently. The biggest win will most likely be for the POST payload (multipart) parsing because 5.4 is faster on array/strings. The good point is that with PHP farm, you can run both 5.3 and 5.4 in parallel to compare :)
