ACZoom

Take a look at Expression Engine! Being a commercial product it has a lot smoother upgrade path than Drupal, and it also has stellar support and documentation. Granted it has fewer external modules available, but the core system plus the modules that are available provide excellent functionality. The new version, 2.0, that will be out later this year (possibly this spring) will integrate CodeIgniter framework and jQuery in the core! I'm doing my first larger site integration with EE currently, and am quite happy with it — and I'm looking forward to v2.0 that brings even more power and ease of use!