Having just finished writing another plugin for WP I now have an even stronger understanding of it. There are definitely things I like about it (UI) and things I don't (API).  What it does right and "not-so-right" can be directly attributed to the project goals.

WP kicks ass in user interface land. Right off the bat the user is given a slick interface with which to edit content. Drupal, on the other hand, requires a bit of massaging and tweaking and setup to get the UI where you want it. It is apparent that the WordPress developers really care about end users and want them to jump in and write content. Drupalers are more focussed on developers and implementers.

Where WP fell short was the API. At first glance it appeared robust and well documented. Upon deeper digging it left alot to be desired. The documentation for WP_query was incomplete. The functions that where documented seemed incomplete. I also didn't like the concept of "this_post", where much of the display side is based on the current post instance. All i wanted to do was query and sort posts based on meta-data. It was not easy! The Node API for drupal blows WP posts out of the water. period.

After spending several nights with the latest and greatest WordPress my verdict is about the same as it has been when comparing with Drupal. If you want a quick and easy site with a simple CMS use WordPress. If you need a more elaborate site with different data types, sorting, aggregation, etc. use Drupal! Same goes for custom development.