greggo wrote:I was of the impression the O'ring is only for lubrication and longevity of the chain and did nothing for cushioning drive train lash from acceleration/gear changes etc.

That's correct, as you will see the rings are on the side of the chain.

You only realy need a non O ring on a track or race bike, when your'e looking for that last last ounce of BHP,on a road bike it dont make much difference.

Totally agree, and the other downside for the non o-ring is that it won't last as long as the o/x-ring chains.

Soooo,

Road bike = o/x-ring chain
Race bike = Non o/x-ring chain