I bought one of these in early 2006 right before I had braces put on. I had heard your gums need to get used to the extra force of water. I didn't want to have to get used to braces and the waterpik at the same time.
I've used it three times a week since then, and it is still going strong. I only do it that often because I read it could cause damage if you use it to often.
I mainly use this to make sure my bands and brackets stay extra clean. I still brush, floss and use one of those tiny brushes that fit between for teeth like normal. The dentist says I do an excellant job and keeping everything clean.
I brush, floss, tiny brush, and then waterpik. I like the extra clean feeling of adding a little bit of mouthwash to the water.
It is a little bulky to leave out on the counter all the time, so I store it under the sink.
The first few times you use one, will probably be messy, untill you get used to it. It doesn't take very long to figure out how to use it though. I let my kids use it once a week, just to help keep their teeth clean. I always worry about how well they are brushing and flossing, even though I check their teeth still.