They are pretty, aren’t they?
I draw many of my production diagrams these days with Enterprise Architect from Sparx Systems. I also like Visual Studio Team System, with its tight integration with process tools. I find that to be top-notch; but Enterprise Architect is my second-favorite UML tool. It’s incredibly powerful and full-featured, especially at the low price of $199 a seat!
EA is the primary UML tool I use in my consulting work, and I often persuade my clients to purchase it as well. It’s also the tool I use when I given UML talks. And although I teach my one-day UML class with just pen and paper to keep things simple, I teach the students to use EA in my longer classes. I have them install the trial version; but by the end of the week, they usually decide to buy it. It’s that good, and I show them how to get productive use of it quickly.