Poseidon UML is the UML tool that continues to disappoint me. I keep rooting for it, because I remember the early days when Jason Robbins was creating Argo UML, and I thought he had some really good ideas on perspectives and critics. But every time I try to use Poseidon, it remains too buggy. The last straw with the latest version is when it locked up on me while I was teaching a UML class. I have a copy of MagicDraw UML and switched back to it then, and haven't looked back.

I'm also disappointed because I thought that after all this time the Gentleware people would have made some significant improvements to the user interface. It still continues to feel clunky.

I see that they have an Eclipse plug-in now, but I think I'll wait until 2008 to take a look at that. Until then I'll keep using my old copy of MagicDraw UML.