Depends on how hard you ride. If your pushing the limits & are getting some front wheel lift out of corners & maybe some slight headshake then it'll probably be worth it in the long run. Also it'd be worth it if your planning on doing quite a few track days.
But if your not pushing it that hard, I wouldn't worry. I've had my R6 for almost 2 years & had never had any headshake or "tank slappers" & I've also been doing some smallish first gear wheelies & haven't had any problems when coming down.
If you've got the spare cash, buy one, if not I wouldn't worry.
I'd probably get one. high speed riding can get a little scary if you don't have it. A small bump at 160mph can really be dangerous if you don't know how to handle the bike or are not ready for it.
if you plan on stunting with the bike, you should get one. Slow first gear wheelies shouldn't be too bad, but high speed wheelies can come down hard some times. Especially if you ride them out, this can cause the front wheel to travel a little bit and not come down perfectly straight.
I think I already told the story here so I won't get into it, but I have a frien who was recently - seriously - injured and his accident would most likely not have happened if his dampener was installed.
If you can afford it, get it it is cheap insurance.