I have been using the new Joomla 1.5.x engine for the main thisMinistry.net site for several weeks now and I like it. The design is reminiscent of the older 1.0.x engine, but updated for the new version. In addition, changes to management and organization on the main admin page (as well as others), make this new version worth while. If you get a chance, take a look at the new update and take it for a spin. I think you will like it.
I will write a more extensive review after a few weeks have passed and I have a fair amount of experience with this product.