I used to use these tools much more extensively when working in more formal, water-fall-ish, slow, more arcane development environments; nowadays I use UML only for documentation after the fact. Specifically, the only place I use UML is after feature X has been implemented and tested, and if it is reasonably complex where just reading the code and tests can get you there, but a couple of high level visuals with some text that describe design rationale would get you there much quicker...well then, I try to be a good netizen and jot that info down. Can't tell you how many times people have thanked me for that. That said, UML is a lot easier to do this with vs. any other visual tool. It is standardized, and most people can read it fairly easily. On a side note, I've found Sparx Enterprise Architect to be the best tool out there for UML.