In this post to the Developer Tutorials blog, Akash Mehta talks about the "version dilemma" that developers face when looking for good hosting - with all of the push towards PHP5 these days, why is it that so many hosting environments are still running on PHP4?

If you purchase a cheap hosting account with many of the major web hosts around today, chances are they will be running PHP 4. The problem for web hosts is this: the PHP community may have moved on from version 4, but a lot of the code out there hasn't.

He recommends one solution that several hosting providers are starting to gravitate towards - offering both to their customers and allowing them to switch between them (via something like cPanel).