Review (5/5): Half the cost, but more convenient than a regular Sonicare
Pros: half the cost of a Sonicare w/charger, less bulky
Cons: None so far
First of all, I should state that I have owned this product for over a year, and I am still giving it five stars.
Here's why: I had a Sonicare Advance for about three years and it worked well during that time, but at the end of those three years I had to keep it in the charger at all times or it would die in the middle of brushing. I was sick of lugging around the bulky charger any time I traveled, so when I saw the AA-battery model at Target for $40 I scooped it up.
Now instead of having to rely on an internal battery and a charger, I just keep four rechargeable AAs that I swap out when one pair dies. This isn't something I have to do very often--a pair of AAs lasts about a month (that's with two two-minute brushings a day). I have also not had any water damage, so the brush still works as great as my old Sonicare ever did. I do try not to get water on the brush and dry the entire unit whenever I finish using it. In addition, I take it apart once every two or three months and swab the O-ring with alcohol to keep it clean. This seems to be all of the maintenance needed to keep it in top condition.
So, if you want a good Sonicare brush that takes up less space and is easier to travel with, I highly recommend this model. I recommend cleaning it once in a while and trying to keep water out of the insides. I acknowledge this might not help if you get a bad unit (as many reviewers seem to have gotten), but mine has been great and I figure it can't hurt!
UPDATE: I have now owned it for a year-and-a-half and it still goes a month on two AA rechargeables. Even though I stopped doing the maintenance described above it's still working like new.