Since I use floss regularly, I had no difficulty with the water jet. You should just be careful to keep his mouth closed, otherwise you have to clean the bathroom mirror :-).
My girlfriend used very irregular flossing and had at first uses the Airfloss easily bleeding gums and slight pain in some places. This has, however, done for about 1 week.
The Airfloss fun and one is after about 1min cleaning the interdental spaces ready. Philips indicates that 1 full water tank withstands 2 cleanings, but agrees not so. Pro Cleaning 1 full water tank. You can also take mouthwash instead of water.
I use the Airfloss every 2 days. A complete replacement for dental floss he's not my opinion, therefore only 4 stars. I use every 2 weeks additional time flossing, I am still very pleased with this unit and can recommend it with a clear conscience!
A little tip: Airfloss and Sonicare charger is identical, ie you only need 1 charger in the bathroom ;-)