I have an Oral B Professional Care 1000 model which works fine and was on £30 with 2 heads. The more expensive models have LCD's, more brushing modes and such but it just seems like a gimmick to me. The 1000 model and most others change the vibration briefly after 30 seconds to let you know to change position until you reach 2 minutes.
I've noticed a big improvement since switching to an electric one, the brush head is about 1/3 the size of my manual one and I use far less toothpaste now. I can reach to all parts of my mouth easily now thanks to the smaller brush and my teeth seem to be much whiter than when I used a manual one.
More money does not equal a better toothbrush, I think most dentists will agree that a basic electric toothbrush is sufficient.