I use the Obeo UML Designer that you can find in the Eclipse Marketplace.
It goes very well together with the Acceleo toolkit for MDSD.
I think the major selling point for any modeling tool is that it has to be able to produce an output that can be fed into your toolchain.
I have never seen models that just exist for pure documentary purposes survive more than two or three cycles in a project. That sort of stuff usually never works, because the changes in the project are executed first and then the model is adapted. This kind of work is rightfully regarded as either braindead or luxury (depending on who you ask).
The correct way is that changes in the project must be driven by changes in the model.
