If you are typing, it is customary to hold a meta key (e.g. Shift) and momentarily type the key for the symbol you want. You often hold the shift key longer than the momentary press of the symbol key, but this causes the key repeat to generate lots of key presses (e.g. Deleting a whole line when you just intended deleting a character!).
Besides this enhancement it would also be great to be able to set an appropriate key repeat pause and repeat rate in preferences. Having written an ace emulator myself I know this can be a bit tricky, but its possible (I think I may have patched the rom at load time for this).
Btw, thanks for the app. I love the ace!