I am not trying to stir up the nest here, but I do want to share. I have been on the Honda Forums since 2006. With the 8th Gen Ridgeline, CRV, 8th Gen Civics and Si, and the 8th Gen Accord. There are literally thousands of posts on Fuel use. Will be considering seriously trading my 09 Coupe for the CRZ early next year.
I did try to switch to 93 on the Ridge with no perceived difference in performance or mpg's. I also did try 87 on my two 06 Si's and had a definite perception of deteriorated performance (no knocks though). I tried 93 on my two 08 Accord V6, again with no perceived changes or mpg's.
Now, I have switched to 93 on both my 09 Civic EX-L coupe and my 2010 Civic EX-L Sedan the last two tanks. I can truthfully say: I perceived a smoother running engine, lesser press on the accelerator to reach my normal speeds, I gained 1-2 more mpg, and very happy overall with the improvement in performance of both vehicles. Worth the extra two bucks for a tank of gas.
I've read most arguments, Pro and Cons, of switching grade of fuel. I am not claiming anything one way or the other. I only want to share this. The Honda manuals on all the above vehicles (except the Si's) does say "recommend 87 Octane OR HIGHER". I understand that to mean, "at minimum, use 87 Octane fuel" I am never satisfied with "minimums". But, that's just me.