I didn't vote because my answer is "It depends." In a lot of parts of the country, you won't be able to get flight following for flights under 20 nm because you just won't get high enough altitude wise to be in radar contact. Even then, it depends. You aren't wasting ATC's time by talking to them, and most facilities appreciate having you talking to them rather than just bombing around. On the other hand, if I'm going on a short flight, it's good VFR and I'm looking out the window, I might not care.
I'll typically get flight following for a maintenance flight, because I'm looking at gauges and that way I have another pair of eyes watching out.
When I'm on a XC, I'll typically get flight following for 50 nm or more, or if I'm going into a Class C or B. Sometimes I don't feel like it, and so I don't.
It's never a bad idea to get. Just remember to focus on flying the plane first. I know some people who avoid getting flight following ever because they're afraid of radios. Not smart.