You can see the PDO Basics entry at wiki.cc here. PDO unifies the various PHP RDBMS function calls; database API abstraction in PHP is a Good Thing.
But PDO brings something I did not expect: table instrospection. You can get meta-information about the statement results that tells you what the native type, size, precision, etc. are for the returned columns. This can make automated type-checking and conversion super-easy. Just one more reason I was lucky to think of making Solar PDO-ready.
Hey, PDO guys: neat stuff, and thanks!