Biggest age difference I've experienced while dating was being with a 22 year old when I was 34. Age wasn't a huge factor, though it was odd to be closer in age to her parents than I was to her since they had her when they were both young.
As for just hooking up, there was a similar age difference when I was in my early 30's and she was a married woman in her mid 40's. That was just for carnal fun and she was a dynamo, so I was just glad I could keep up.