You can see the user reviews from Android Market on these pages:
My name is Mats Erik from Norway. I would like to tell you that I am very satisfied with Tennis Math, and i hope you will release a version for iPhone or Windows mobile very soon. I've only borrowed an Android device (HTC mobile) from a guy a know, and used it in two matches. However, I found it much easier than using the old fashiond pen and paper method, and therefore it would be nice if you released a version for iPhone. I am a 16 year old who playes tennis 12 hours a week, plus tournaments or training during the weekends, which is quite much. I want to raise my level of play, an that I can do with a tracking system for the statistics in my matches.
since meanwhile four weeks I am using the HTC Hero, but I'm still in the orientation phase. Joining a tennis tournament last weekend my children were playing, I wondered whether it might be possible to count the points in a more elegant and safer way than always keeping them in mind. A quick call of Android Market yields Tennis Math. A brief trial run with "ScoreOnly" mode and I was ready prepared. Following the upcoming match was no problem and mastering small problems like incorrect input and their removals was done on-the-fly. Finally after the game, the small statistics astonished my kids. What? How? What is? How so? Also the surrounding friends demanded their urgent need. But sorry - no Android, no Tennis Math yet.
Meanwhile I have practiced a bit more with "Full scoring" mode and I will give it a try in some upcoming non-critical match. I am looking forward to examine the full match analysis afterwards.
In summary: a superb application with desirable usability, transposed from practical expertise and very addictive.
The only thing I currently miss is a statistics export function, perhaps using something like CSV-format. No necessity of feature bloating, simply the opportunity to get collected data out of the Hero.