I'm 42, and my boyfriend is 24. I find that we have very challenging conversations about a variety of topics, usually ranging around political and philosophical subjects, so there's no maturity issues there. We both work with computers, too (he's a network technician, I'm a developer), and we're both science fiction fans (we met at Dragon*Con last year and have attended three other cons together over the past year).
The only drawback, really, is that we're 1000 miles away from each other and have to talk over webcams. I'll probably be visiting him for New Year's, though, and we have tentative plans to go to next year's Worldcon in Melbourne together, finances and vacation time permitting.
When I was still single, most of the guys I dated were two years younger than me, by some odd coincidence. The two exceptions I can think of were someone I met back in 1998 and still keep in touch with (he was about five years older than me) and the one I mentioned in the anecdotes thread, who was 23 at the time (so I guess he would be 25 now). The younger one had some issues, I think, though - he stood me up for what would have been our last date, ignored my phone calls over the next week or two (I was trying to ascertain whether he was okay - for all I knew he might have been hit by a car on his way to meet me), and then broke up with me by defriending me on Facebook and sending me an email the next day.

Not exactly a paragon of maturity, there.