I have had one for 13 years and do not regret buying it. The advantages are never running out of hot water, lower gas bills since you are not reheating the water in the winter and you gain more space wherever you place it.
No matter where you research the tanks the same disadvantage keeps showing up: It will not have the capacity to run hot water in several locations. Stop and think about how many times you are going to require a large volume of hot water in more than one location (not while I am in the shower). The only drawback that I have ever experienced is that you cannot really set the temperature for the dishwasher requirements as this tends to cause fluctuations at the tap. If you have small children in the house this turns out to be an advantage to prevent scalding.
The advantages far outway the disadvantage. If you live far enough north, a holding tank is also a good idea. Good Luck!