The 10/11 and 11/12 are the exact same besides colors. The 12/13 changed to a slightly different toe strap system. I haven't tried the new ones so I can't comment on them, but I've owned 10/11 and 11/12 versions and they have worked great for me. I went through the same thought pattern and decided it was not worth the extra $85-$110.
Talked to another K2 rep this morning and he said the toe strap is indeed different on this year's model. He also said the new toe strap could be purchased for $42 but he wouldn't be able to confirm that they're compatible with last year's binding until Monday morning.