Dynamically Typed has a new post today asking the question: "Just what is PHP 5.1's killer feature?"

PHP 4 didn't really catch fire in terms of real-world server support until its first major update, version 4.1. Will the same be true of PHP 5, the first point release of which is now in its early beta stages?

PHP 5.1 Beta 1 has been out for ten days, and Beta 2 has just become available. [...] At this stage, PHP 5.1 is not looking to be quite as spectacular. Some enhancements to Perl regular expressions, a few extra array functions... nothing to write home about. But there is one significant enhancement to PHP in 5.1: PHP Data Objects (PDO). His suggestion is that the PDO library is the reason that people will make the upgrade to PHP 5.1.

What do you think? Will you upgrade when the full PHP 5.1 is released so that you can take advantage of the PDO library? Or is it "just another abstraction layer"?