Free not necessarily in the GNU sense, but in the sense of freeware. I've tried the following UML modellers:

Poseidon
UML Sculptor
JUMLi

Well, I don't like any of those. Poseidon has tons of features but is so incredibly slow that it's a pain to work with. UML Sculptor isn't even a finished product, some things still don't work and the feature set is meager at best.
JUMLi, well it's somwhere in between

Are there any GOOD UML tools? Has anyone tried the Eclipse UML plugin?