I have owned quite a few battery powered or rechargeable toothbrushes and this is definitely the worst.
It has, in my opinion, two big problems: the fact that it is not waterproof and the annoying ability it has to go through many, many batteries very fast.

My Spinbrush's consumes a lot: I brush my teeth three times a day and a set of batteries only last about two weeks. I am not sure if it is defective, but it would certainly be expensive in the long run. Please note that I used 'would' and not 'will'. I don't expect this toothbrush to survive as it is certainly not waterproof.
I use the term waterproof loosely here, because I don't mean that you can't take it into the shower and use it there, or that water will get into it if you drop it in a bathtub full of water -that would be asking a lot. What I mean is that, during normal toothbrushing activities water collects into the battery case quite easily and quickly.
If you are very careful you can empty it, dry the batteries, leave the toothbrush open and let it dry, but it is a bit of a pain if you ask me (and the case is also hard to open, which doesn't make things easier).

It is quite a shame, because as a toothbrush, it does a decent job and leaves my teeth feeling nice and clean. Unfortunately the two big cons make it a tool I would not recommend to anyone.

After my Oral-B battery brush finally died, I decided to try the Crest brand battery brush. Big mistake! First of all, it took 3 different people to finally get the battery cover off to replace the two batteries. I used cooking oil on the plastic parts so it would come off easier the next time the batteries needed replacement. That did help, although I was surprised how quickly this would be necessary.

The brush does spin quite fast and with a fair amount of power.

Compared to the Oral-B, this is a poor design....plus it uses 2 batteries instead of one.

Get the Oral-B. A much better buy, only one battery needed and better quality.

At first, I hated this toothbrush. It seemed to consume batteries way too quickly and leaked from the top after use which made a mess on my bathroom counter. After the first one finally broke, I figured I would give Crest the benefit of the doubt and get another one because it was so cheap. Best decision I've ever made. The new brush is fantastic. Not one complaint about the replacement. It still consumes batteries quicker than I'd like it to (needs replacing about once every 3 weeks) but is a small sacrifice for the brush being so cheap. It cleans my teeth extremely well. I could see a difference with the 2nd cleaning. I switched from a manual brush, so of course I expected a little better cleaning, but it exceeded my expectations. By teeth actually shined in the light instead of just reflecting the light. I noticed that my teeth were substantially whiter after about the 1st month of use. Very compact design and is pretty quiet. If you plan on buying one of these and are switching from a manual brush, be warned that the vibrating takes some getting used to, but is easily overcome. I highly recommend this to anyone, and am using it as stocking stuffers for my family. Combine this toothbrush with Listerine antiseptic mouthwash and Colgate Total plus whitening toothpaste for long lasting fresh breath and sparkling white teeth.

I Purchased the Crest Spinbrush about 12 months ago and it has worked very well for me. It cleans as good, if not better than the Sonic Care toothbrush that I used in the past and they are really cheap. You can simply purchase replacement heads when they wear out. It runs on two normal alkaline batteries and I use rechargeable batteries to save money. The toothbrush has a very good battery life and can go months without having to replace the batteries. My teeth have never felt cleaner. I highly recommend the Crest Spinbrush.

The design must be defective, because I'm reading review after review where people have a similar experience. My spinbrush failed after just a few days. It seems that water somehow got into the battery compartment and quickly corroded the electronics. I've owned previous models of spinbrush and they held up pretty well. It seems that this new 2-speed variety of brush has a design defect. Definitely not recommended.