It is easy to use and does a good job, even getting debris out of my teeth after flossing. It is very messy when using. One annoyance is not having a charging light - there is no way to know when to charge it or when it is done charging. I would give it 5 stars if it had a charge light.
This is my second one, bought to use while I travel. I already use an ac power version for home use. The portable is far less powerful but adequate for travel.
I recently purchased the WP-450 and it really cleans my mouth. It is easy to use, light weight, and portable for travel. It also doesn't take up as much space on my bathroom counter as the ones with the tank. You will have to add more water sometimes. The various tips that came with it are useful, but I wish they would have included the Pik Pocket Tip for my periodontal issues. They are available from the Water Pik online store therefore I will order some. I am very happy with my purchase.