I think anybody that has done the 520 conversion and dropped a tooth in the front can tell you that it makes the bike WAY snappier. My 06 gsxr 1000 was a raped ape with a tooth off the front...If however you like freeway riding, I would think about it before you do it, or at least maybe NOT do a chain size change, so you can just swap the front sprocket back if you dont like it. Also, as im sure you are probably aware, the speedo will be off a bit.
I think its still considered the biggest gain for the $$$...