i didnt get a new stem but i got the trailtech xbars with the new dash for the vapor and the key goes on the back side of the bars, just enough room to get the gas cap off. I like it alot. The bars are a little shorter than stock but the clamp raises it up so its about stock. I think it fits me better now.
I thought it was very easy to do. I found that standing the bike up on end and removing the skid plate to be the quickest way. The directions are good but you will have to bend the cable guide toward the motor a little bit to get the proper play in the cable. I really can't think of any cons however I never even rode the bike with stock revers knob.
Ditto what Jay said. I didn't take anything off (skids or plastic) and had just a little trouble fishing it, but would do it again that way if I had to. The mounting bracket will need tweaked like Jay said, too and the adjustment nuts ran all the way in. After a little usage some more play in the cable will develop. My lever sits a little closer than what it's supposed to, but it's easier to reach here and gives me enough room for my Vapor's handlebar mount.