It would be great to have the choice to make or not a game using the x2.
For performance and the size of the IPA, it could be important to have the choice.
For my exemple, my game (who's not really optimized), has a size of 16mo.
Without the x2, it could be 12mo.
I agree the fact the x2 on the iPhone 4 is really sexy, but I think for some game, it's not important.
A box to check ? Stencyl generate x1 and x2, and if the box is checked, the x2 atlases don't go in the ipa ? only for compare the performances and the RAM usage it's THE option we need to have. (Bigger atlas so, bigger RAM usage)
I think it could be really great.