that is one of the most noticeable (seat of the pasts wise) mods you can do.
note that your highway cruising rpms will be higher
note also that the speedo and odometer may end up a little off, even if you get the gear that is supposed to correct for it. this is because of the way adding or removing teeth on the speedo gear changes the speed the speedo gear spins, which is the idea, but the change is often not exactly the same as the change that happens at the rear, so the speedo will be a few MPH off.
at first, i didn't care if my speedo and odometer were off, but as time went on, i cared more.
there is (or at least used to be) a device called a speedcal that you can get that more accurately corrects the speedo if that is important to you.