Got this to replace an obsolete model I'd had for 20-plus years. The new one seems a bit flimsier than the old one; its reservoir holds 40% less water; it doesn't (the old one did) come with a wall mount. None of these are fatal flaws, but I doubt whether this unit will last anywhere are long as the old one; check back in, say, 10 years!
This is my fifth unit over the years. Worst design ever. Top is problem. It has to be removed completely and put back on with precision or it will fall in reservoir. Also had to run vinegar through it for almost two weeks to remove unpleasant taste. On a good note, works as well as all others I have owned.
Bought the waterpik on advice of my dentist and the person who cleans my teeth. Took some getting used too but once I didn't make such a mess was surprised by its effectiveness. Use it every night after brushing. Mouth feels real clean.