I have an app which runs excellently on an iPhone 4, and comfortably on a 3GS. Is it possible to target only the 3GS/4 and not the 3G? The 3G just freaks out when I run it, all sorts of graphical glitches, crashing, low fps etc, I don't even want 3G users to see the app on the store. I can't really 'tone down' the app to use less memory/power for the 3G, it would remove the main purpose of the app.
The only way I have come up with is to adding multitasking as a requirement for the app in the info.plist, but this seems a little hacky.
Also, is this likely to get me in trouble as far as submission goes?
Add "armv7" to the required device capabilities of your app's info.plist. Only the 3GS and newer use that CPU architecture. An app requiring armv7 won't even install on a 3G and other older armv6 devices.