argoUML - Java

I've long liked argoUML, but I've found that its complexity doesn't fit my problem sets. I really like the design critiques, but I find that I get side tracked too quickly if I focus solely on those and I've yet to learn the balance in controlling the demands of the critiques

Bouml - Windows / Unix

I really liked Bouml. Nice design tool, but I found that it was a little sparse on the learning curve. If you know modeling, then it probably won't bother you, but if you are still figuring out the widget differences in the various UML diagrams, you may feel lost.

Umbrello - Linux only

There are several things that I really like about Umbrello and a few that I don't like. I like the fact that the project file is XMI (an XML variant associated with UML). I really like the UI and placement / alignment magic in the UI. I don't have to futz too much with the widgets to get a reasonable diagram. I especially like the rich output language set.

Unfortunately, I find the 1.3 version to be a little buggy. Once you figure out the .XMI file format, you can fix some weirdnesses, but there are times where it is safer / faster to toss an entire diagram and recreate it than to try and figure out why certain objects cannot be added (when they can be on a clean diagram).

2006-06-13: While it still hangs and occaisionally crashes, I did figure out why it won't add classes to a class diagram due to deep containment. Apparently, I had started to mix UI metaphors and had started moving classes around and started creating a deep set of inner classes rather than normal classes in a package hierarchy. Umbrello correctly refused to add classes that were nested more than three levels deep. When I saw the error of my ways and switched to package containment, this problem went away and I was able to drag my classes back onto the class diagram.

Overall, I like Umbrello the best, but that just may be because I'm on Linux the majority of the time and because I use many of the languages supported by the tool.