So the installer doesn't work yet, but for MySQL everything else should. For those who want to try it out, you can check out a copy of Drupal with the new database code in it from chx's public svn repository: https://4si.devguard.com/svn/public/pdo . A proper patch will be forthcoming as soon as the installer works, which should be Very Soon Now(tm). For a complete list of the new features it offers, see: http://www.garfieldtech.com/blog/drupal7-database-update .
If you want to help with the installer, let chx know so he can give you commit access to it. :-)
This patch will also deprecate about a half-dozen old feature requests for the database layer, as it works a whole bunch of features into one cohesive system. I'll go flag those as duplicate shortly.