I tested a couple of "Tennis Stats" apps and this one seems to strike the best balance between fulfilling the need of beginner and advanced players. It is very easy to use. I use all of the functionality except tracking ball placement since my sons play is not quite at that level but it is good to have that option. My wife only likes to keep track of the score which is fine because even at that there are certain stats I can still follow.
And speaking of stats, they have been very helpful in taking away the guesswork of which shots are working or not.
I definitely recommend it for all level players (and parents).
Tennis Dad 2 about My Tennis Stats, v2.1.3