Hi @Grant Palin:
My use of WordPress is almost exclusively CMS, and the other software I have experience with is Drupal (2 years ago, but have continued to follow it) and DotNetNuke (5 years ago, and I haven’t looked back.) I also reviewed Joomla about 3+ years ago and found is to be both too complex and too inflexible, so I never seriously considered it.
Anyway, I can only speak with any real authority about how WordPress compares with Drupal as a CMS, and as luck would have it I wrote a blog post about exactly topic last week: