Review (5/5): Nice improvement
This is a nice improvement to the Sonicare line of brushes. It appears to be their response to the Oral-B Floss Action line of brushes that have a "paddle" to help get between teeth. This accomplishes that goal with an plastic insert in the middle that helps direct the toothpaste between your teeth.
I use both the Sonicare (Healthy White) and the Oral B 5000. Both have their pluses and minuses, so switching between the two gives me the best of both worlds.
The Oral-B arrangement of paddles does a better job in getting at the gum line without discomfort. The Sonicare Hydroclean's bristles are stiffer and I find that they irritate my gums when used several times in a row.
But, the Sonicare does a better job in cleaning stains between teeth. I'm a tea drinker and getting the stains out between my front teeth has always been a chore. The Hydroclean works very well - noticeable improvement over the Sonicare ProResults and the Oral-B.
These only come in the standard size. The ProResults has a smaller version that is great for getting at the tight spots. But, I assume that a smaller version of this would not function well since the plastic insert would have to be very small.
If you're a ProResults user these are well worth trying out. If you have tender gums you may want to alternate between the HydroClean and the ProResults (or, as I do, with the Oral-B. The Oral-B also makes a super soft brush if you have very sensitive gums. Hard to find, but works very well).
Keep in mind that nothing takes the place of flossing. No matter what you use, you still need to break out the floss to keep your teeth healthy!