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.
**Scotts makes a very good one**