I bought the water pic three weeks ago and I love it. My gums are in much better shape and I can't believe how much food is still in my teeth after flossing.
I did an extensive search for a new flosser and Waterpik WP 100 was the best option. So far this has been a great addition to my oral health care. I'm not crazy about the noise but I expected as much. You'll definitely feel the difference after a few uses.
The pik is a useful tool for cleaning purposes but I find not as much pressure as the single unit with refill in the handle. Can be messy and have to make certain that you are over the sink when cleaning.