Hmm. this morning the support team at the data center where we have our server (and who we would hire to do the PHP upgrade) doesn't recommend going to 5.3.3 but to stay with 5.2 for now. I think that should suffice. Most of the apps we want to upgrading like phpMyAdmin, phpPostGresAdmin, XOOPS etc are asking for at least 5.2...

"PHP 5.1.6 can be upgraded to 5.2 with minimum issues as 5.2 appears to be a more stable version of PHP. PHP version 5.3.3 has many well known bugs and it can cause some problems for the applications that have been configured on your server. We can however, upgrade your PHP to version 5.3.3 but an upgrade to version 5.2 is recommended. Please let us know how to proceed with this.