Well, not so much anymore I don't think. It's the sort of thing I'd be more likely to hear from my parents or grandparents than from someone my own age, and even then you don't hear it very often.
Normally it's an expression for when events flow smoothly or a task becomes more simplified than before. For example, if a friend was going to have to take 3 buses to go somewhere on a tight schedule, but you happen to be going in that direction anyway and can give them a ride, you might say "Hey don't worry about it. I'm going that way, I can give you a ride. You save bus tickets and time, we stop at Tim's on the way, and we both get to where we're going on time. Bob's your uncle".
It's a poor example, but that's my understanding of how it's used.