Review (4/5): Good for the price.
For around 15 bucks, this rechargeable brush does a good job. My teeth feel cleaner compared to using a manual brush. I haven't used any of the more expensive ones (those over $100), so can't really say how this compares to those. However, compared to manual brushing, this is easier and more fun to use. So you actually look forward to brushing, which I guess has to be good for your teeth in the long run.
As for the brush head, I think its small enough that it can reach those wisdom teeth at the back, but its large enough to fully surround a molar. To get a feel for how well it scrubs against my teeth, I gently pressed it against my tongue and I must say it does a much better job than a manual brush.
The 2-minute timer is helpful, although I go about three minutes to satisfy myself.