I teach computer science and have been incredibly frustrated by the commercial UML tools. My students got caught up in the complexities of Rose and Together, decided that the complexity had to be there for a reason, and then reasoned that their most important work product was diagrams, not a working program. (The same thing happened to me when I was a manager at a startup, but that's another story...)
And I have to agree that vendors are idiots. I gave up on Together when their trial/academic version came with a license key system that was even harder to use than their product.
Unfortunately, ArgoUML/Poseidon didn't work either for me because the sequence diagrams were broken. (They may work now--I just noticed they have a new release.)
I got so frustrated that I ended up writing a tiny UML editor program with just the features that I and my students need. It was so easy to do that I once again must agree that the CASE vendors are idiots, with 99% marketing and 1% technical staff. See http://horstmann.com/violet.
I also agree that a ROCK-SOLID reverse engineering facility would be immensely useful. But reverse engineering that ALMOST works is completely USELESS. Of course, implementing reliable reverse engineering is actually hard--much harder than selling overpriced tools to clueless managers. Sigh.