My daughter just turned 4 and has a Leapster. She LOVES it and asks to play with it all of the time. The reason I like the Leapster is because it isn't just games, it is also teaching her how to write her letters, match shapes/numbers/letters, etc. She has 4 games for it right now (there are more I could purchase for her age, I am just waiting for Santa to get them for her) and the Disney Princess one (Cinderella & Ariel) is by far her favorite. She also has Pet Pals which she loves to play because she can make the dogs do tricks and wash them. I haven't looked to see if there are a lot of games for 7 year olds, as I haven't reached that age yet. :)
When I was researching what video system to get her, I read that the Tag (pen) was cheaply made. You can also only store a certain amount of books on the memory card, so when your child wants another book, you have to erase a previous book.
I have no regret about buying her a Leapster and I have recommended it to several people. One of my favorite features is the fact that you can plug it into your home computer and see where she is at educational wise and what areas she has grown in since starting to play it.
Good luck! I hope this helps.