Review (5/5): totally great
Pro
Cleans teeth really well through high-frequency oscillations
No rotating parts
Brushhead slightly smaller than manual brushes
Con
May not be sealed as well as it should be
Brushing power decreases as alkaline batteries run down
Discussion
Before I bought this brush, I read the 1- and 2-star reviews complaining about corrosion, and the one reviewer who cautioned against reviewing too soon after purchase. Well, I've been sitting on this review for more than two years. No water intrusion, no corrosion, no need to wait any longer before posting.
After the first use, I was convinced. After the first 2-minute session, my teeth were as clean as from an office cleaning.
The e3000 is intended for teens and preteens, thus it has a slightly smaller brushhead. This makes it less prone to bump against teeth (which IS disconcerting!) and the small size encourages keeping the brush moving. There's no need for 30-second reminder beeps, because you will have touched all surfaces "equally" if you keep it moving the whole time.
The toothbrush uses a strong permanent magnet at the bottom end of the brushhead assembly. This magnet is deflected in a resonant mode by an electromagnet inside the handle, and torsion waves are sent to the head. It's efficient and there are no rotating parts. Regular alkaline batteries last at least a month; my next set will be NiMH rechargeables. The handle is larger and heavier than might be expected, probably to counteract the oscillations of the head. The buzzing is not at all unpleasant, as I also had feared.
Before switching to the Sonicare I had used the Crest SpinBrush for 10 years, and the last straw was when I rinsed off the SpinBrush and black flakes fell out into the sink, and kept coming out as I rinsed and shook. I'd been cleaning out the crud that I could see, but what I hadn't counted on was the stuff that I couldn't see! The openings in the SpinBrush accumulate crud, and since you can't see it, you don't think about it. My breath is not as nasty since I started using the Sonicare and ditched the SpinBrush.
I've applied a small amount of clear silicone seal to the flexible boot which tries (not entirely successfully) to seal the top of the brush. A couple of dabs seals the inside of the top chamber, and the tiny amount of water that gets inside that chamber does no harm. There's only one place for crud to hide, and that's between the torsion shaft and the rubber boot where it emerges from the cap. The brush head gets rinsed off with every use, and there are _no_ crevices in it. After two years, it just might be time for a new brushhead... or maybe not.
Reading through the reviews here on Amazon before purchase was very helpful, and it seems that all those who experienced early failures had water intrusion. The addition of clear silicone to the marginally sealed areas (and if you must, silicone grease to the O-ring) fixes this one design weakness. Make this modification yourself and enjoy it for a long time!