Sigh, this is going to be a sad tale. Unfortunately, I haven't yet found any up-to-date software that's productive, easy to use and supports standardized UML. My only hope so far is Umbrello, amde for KDE. I'm not happy about this, KDE in Gnome requires more libraries and a probably not so well done integration. This leads me to a point were I should definitely think about getting more KDE software because I'll need to install it's libraries for Umbrello.
I don't like how definitely useful UML software is focussed on commercial use. I mean for me, as a single person, I don't need all the components. And if I can get it somehow, I'd need to live with the fact that it wants me to buy the most pro version ever on all occasions.
I see where this is going. And it's sad to say this.