backslider, it all depends on what you want to do. Don't even think about drawing sprites as polys if you want full 60 FPS but other things are very fast.
I've attached a little proggy that I used to test what my 3rd generation iPod Touch was capable of in terms of alpha blended, rotated and zoomed DRAWSPRITE calls. What it does is draws successive 160 x 120 sprites on the screen while rotating them and zooming them slightly. If the frame rate drops below 60 fps it won't increase the sprites, therefore the maximum number of sprites it reaches is just one more than it can cope with.
On my new iPod Touch (600Mhz CPU, PowerVR SGX GPU) it manages to get 85-86 sprites without running into problems. Adjusting for clipping (some parts of the sprites won't be displayed) That means it can cover the entire screen approximately 10 times over with successive sprites.
If you, or anyone curious about this, could compile the app to your device and let it run until it reaches its FPS ceiling it would be interesting to see how many sprites it reaches before stopping. I'm guessing an iPhone 3 with OS 2 will reach about 30-32 sprites.
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