It's a fine line between better cruising revs and having a negative effect to acceleration, I've done this mod and did notice a difference
The difference was noticeable on my old 790cc T100 'cos as HT says, they had a 17 tooth sprocket fitted as stock. From memory it dropped the revs by around 400 rpm and made you less likely to search for the non existent "6th" gear. Fitted one to my current 2012 865 SE Bonnie but they are totally different in gearing to the old 790's. If I remember correctly, the old bike was virtually at 4000 rpm at 60 mph with the 17 tooth but the SE is almost at 70 mph @ 4000 rpm. To my mind there was no advantage as it made no real difference to me so I stuck with the 18 tooth one.