I know a guy who hits these weird "roller" serves. The serve goes about 50-60 mph, but he imparts topspin on the ball plus a high trajectory so it gets a really good bounce. That serve is really good for what it is considering most people put way too much side spin on their ball causing it to situp after the bounce.
That type of serve wont be consistently exploited much until high levels of 3.5 play.
"In the 1980's two men dominated--sometimes each other, most of the time everyone else."