When thinking about using a waterpik instead of flossing here are some good pros and cons to consider.

Pros: Waterpiks are effective,  They can be faster to use the flossing,  Waterpik normally come with multiple wands and different color so different family member can have their own just like a tooth brush. Great for braces, Flossing with braces can be difficult waterpiks are offer suggested by Orthodontic dentist. Adjustable water pressure, You can get cordless waterpiks. Waterpik are good for people who may not floss well and are having gum issues.  Anything that will make you take care of your teeth and gums better is helpful. 

Cons:  Cost can be a factor since they can run as high as $50 – $60 dollars. They do brake down some not even lasting a year depending on how well you take care of it. Hard to always see what you are doing which can cause you to make a mess.  Looking in the mirror can also be difficult as the spray tends to go where you are looking.  They can be too noisy. Waterpik take up to much counter space which is bad if you have a small bathroom.  If you are not careful the time you save in flossing is taken up by have to clean sink and counter tops from water mess. If you are not careful they may over time loosen bridge and crown work. Over use like anything can cause more harm then good so make sure you use as directed. 

If you are not sure what is best for your oral health care talk to your dentist see what they suggest. Having good advise from your own personal dentist is worth taking in and thinking about as a deciding factor