I'm currently dating a guy 4 years younger than me. I guess I'm at a quarter-life crisis and re-living my young adult years w/ him. We're having tons of fun. No really, he's a bit more mature for his age (isn't that unusual in some guys??)
In my experience, I tend to go for older guys, the oldest was 29 and I was 19 at the time. I appreciate maturity because I'm highly mature for my age (now I think I'm more closer to my age than I was when younger).