I use Together Control Center. An excellent tool, which among other things provides keeps the UML and the source code in constant synchronization. I find it extremely useful for that very purpose.Surely a tool that spits out UML-like diagrams of the current code would be very useful to spot architecture flaws introduced during the refactoring process.
However, I would point to something Martin Fowler said:
We're kidding ourselves if we think that UML is automatically more intuitive for everyone. Or even for most people.... some people find software diagrams helpful and some people don't. The danger is that those who do think that those who don't should do and vice-versa. Instead we should just accept that some people will use diagrams and some won't.