Superb product
I've been using brand X for years, and liked it, but like everyone else resented that the battery determined its useful life. I decided to try a battery operated unit with which I could use rechargeable NiMH batteries.  I got my hands on both brands and the vibration in the Sonicare is visibly more aggressive in its cleaning action without damaging teeth or hurting gums. The vibration hums instead of rattles. Try it -- you'll see what I mean.<br />As I came to Amazon to shop for my product, I was turned off by the frequent bad reviews about leakage into the battery compartment. I frankly do not know whether that is still a problem, as one reviewer said he believed Sonicare had solved the problem.<br />When I ordered my brush, I also ordered an inexpensive container of O-Ring lubricant. No need to buy food quality or scuba quality, any lubricant will do. Vaseline may well do the trick, but petroleum is bad on rubber, and since I do not know the material on the Sonicare O-Ring, I thought it better to spend a couple of bucks for a small, inexpensive tube of silicone lubricant.  O-Ring lubricants serve three primary purposes: first, it keeps the o-ring supple. Second, it lubricates the surface to make it easier to reassemble the cover without damaging the o-ring when you replace the battery. And third, it prevents leakage.  I noticed that the unit I purchased has a flat stand so that this unit is laid on its side when it is not being used, instead of standing upright where any water remaining in the head can drip down and find its way into that battery compartment. I have not had my unit very long, but I intend to watch that battery compartment and will update this review if my brush leaks despite my precautions.<br /><br />I fully expect, however, that this Sonicare Extreme will outlive the 2 1/2 year warranty.<br /><br />I did not mention that Sonicare extends their normal 2 year warranty by six months if you go online to register your product. I expect I'll have to tolerate a few emailed special offers for that extra six months, but maybe it will turn out to be a good investment. That's a pretty long warranty for a product that is used as frequently as this thing -- and certainly will outlive the rechargeable units I've been using.<br />UPDATE: I've now had this unit for about two months, and in that time I've replaced the NiMH batteries twice for re-charging. The brush takes excellent care of my teeth and gums -- aggressive without being destructive. Most importantly, the silicone grease I'm using on the o-ring that seals the battery compartment is keeping that compartment clean and dry. I haven't changed my mind -- expect this product to last its full two and a half year warranty, and beyond, since I can just swap out the batteries. We have two of these in the household and both are working like Swiss watches.
Rating: 5 stars