I use the interface on my iphone OS3, and it works fine. Here's what happens:
You select "My games" and pick your game.
Then the board comes up.
To move a piece, you do a "quick touch" to highlight your piece, and it turns green, and then another "quick touch" to place it. No problems. If you pause during this process, then your code kicks which displays a larger square in which the piece is identified. This really isn't necessary in my opinion. I can see my screen just fine. But what is FUN about this is that if you let your finger linger then the apple code kicks and then depending on your finger movement, one of two things happen: one thing that happens is that it gives you the option to "copy" this big box and then you can send this pic of a queen, or pawn, or whatever, to your friends and family by pasting it into whatever messaging you want to do. Another thing that happens is that the apple code kicks in with the magnifying glass. This magnifying glass is not as helpful as your big box for showing the piece.
In my judgment, your code (in which a the piece is displayed in a larger box) is not necessary because the chess board and all the pieces are very readable on the screen. On the other hand, it does give you this unintended side-effect option of being able to copy pictures of the pieces. But, that isn't really necessary or even all that much fun on the fun-o-meter.
If you want folks to be able to see "big pictures" of the pieces, your code works better than the magnifying glass. But if you realize that the board and pieces are easy to read without any kind of magnification (but then again, I don't yet need bifocals on my glasses!) then you should ditch the code.
I hope you find this feedback helpful.