The only way I suggest it to anyone is if they drag only.
Pro's- first the obvious, clutchless shifting, much more consistant, will also help get your bike down the track quicker- i hear ranges from1 tenth to 2.5 tenths depending on the rider.
Con's- W/ the mod trail ridin is out of the question, if u grab the clutch in the middle of a run you are more than likely gonna bent a shift fork.
Those are the only 2 con's I can think of.
I put a 2-5 in my 350 and picked up 2 tenths, it took a few try's to get the gearing combo right to get that, but IMO was WELL WORTH IT!
Remember when shoppin for an ovveride, cheap is not always the best way to go. I have ridden the "cheaper" overrides, and they feel to notchy. Most ppl can hear when I shift my bike because its so smooth- alot of ppl only know I do because of the puff of smoke that my pipes let out.