1) you have almost unlimited memory - if you're not clever with your memory management (eg. UITableView cells) things will look great in the simulator but will crash/run slow on the device
2) some things can't be simulated (push notifications, in app purchase)
3) certain libraries have different binaries for the simulator vs. the device. bugs in one or the other can cause things to work differently
If you submit your app to apple having tested only on the simulator, chances are they will run into a crash/bug when reviewing it causing your app to be rejected. Having said that, it's a great tool for debugging.
1) you have almost unlimited memory - if you're not clever with your memory management (eg. UITableView cells) things will look great in the simulator but will crash/run slow on the device
2) some things can't be simulated (push notifications, in app purchase)
3) certain libraries have different binaries for the simulator vs. the device. bugs in one or the other can cause things to work differently
If you submit your app to apple having tested only on the simulator, chances are they will run into a crash/bug when reviewing it causing your app to be rejected. Having said that, it's a great tool for debugging.