Well,
I learned to ride cleated/clipped-in on a mountain bike, and now that I do, I can tell you that going up hill over rocks (seated) is charming! (I love my seat too; Serfas Curva). I almost feel like I'm cheating in comparison to when I first started riding.

I now have "power" in my pedals and use a better range of gears than when I didn't clip-in. I also up graded this past fall to the Shimano 504's. I recently asked the pro-rider at my LBS what pedals she uses; she also uses the 504's. She said she likes them better than the Speedplay...of course, she X races. Also, hose/wipe your bike down after you ride in harsh terrain. It's an important habit to cultivate and will keep you on top of what is going on with pedals, tires, ect. Then lube as needed. Again, use a product that is not going to gum up the works. I like a teflon based product for parts/cleats and Dumonde Tech for the chain.

Could be that I'm becoming a better ride which makes for a faster, smoother, easier ride. I think if you are a roadie or spinner, you can really tell the difference between cleat systems over a platform/cage riding. Like everything else, take your time, learn from your mistakes and details, details, details!
Terry