I moved from a 2011 i5 11" MBA to a 2012 i7 11" MBA.
The difference is subtle but distinct, and you won't notice it under light load. If your usage patterns center on web browsing, etc., save the money and stick with the i5.
If your usage runs to serious design applications - many of the CS6 apps, for example - then I think the i7 will do much to prolong the useful life of the machine.