That wrong gear thing is killer!
When I started MTBing last year, for some reason I got it into my head that it was "wussy" to use my granny gear -- or even the whole granny ring!
Let's just say I don't have that problem anymore. I live in my granny gear. Well, granny gear + 1, just to give me a little extra oomph on obstacles. It's amazing to me how much more ground I can cover this way.