Coincidentally, yesterday I was coding a script for WP on my local machine and used the array_replace() function. It worked just fine running PHP 5.3 but failed on my site because such function is not available in version 5.2.
This morning I asked my provider about the possibility to upgrade PHP to 5.3 'cause I need it to upgrade my TYPO3 software (released yesterday) that requires 5.3. The response was:
"Cpanel has released php 5.3 in easyapache but there are several features which are missing in php 5.3. As this version has alot of compatibility issues so We can't upgrade PHP version to 5.3.x on our shared environment server as it may effect applications/scripts of many other clients hosted with us like you."
They suggested to move my account to another server and compiling 5.3 on it. No way, I decided to wait until all issues are cleared up in order to avoid any risk with WP new releases and other applications.