jjct1,
After breaking from the Mambo group one year ago Joomla has progressed to version 1.0.11. Version 1.5 is in beta and I just read yesterday that while there will be an upgrade path to version 1.5, it's going to take a lot of re-working to get there and users should not expect a painless automatic conversion like the previous updates have been. Here's a link to one of the third party developers that's talking about this.
Joomla 1.5- What You Need To Know by Phil Taylor
I still recommend Joomla, but it looks like some extra work ahead of us to get to version 1.5.