I ran a 530 chain on my 525 sprocket when I first got my bike and it was unnoticeable in the way the bike felt and responded... then again i was new to bikes...

As far as wear goes, you can expect premature wear, it wore the stock steel down like it was aluminum, but then again, it went about 5k miles like that
EDIT: keep in mind I didn't take care of my sprockets and chain like I do now
, and I didn't even know the chain was different than the sprockets til someone told me. It prolly wasn't too safe, but I didnt die... and the local auto mechanic said people do it when money is tight.. so I dont know what to tell ya... sprockets and chains are pretty cheap right now... why not be safe?

http://cgi.ebay.com/ebaymotors/ws/eB...K%3AMEWAX%3AIT

35 shipped!... you can get a decent o-ring for 50 easy.
thats an 85.00 investment you won't regret down the road.

 

So long as your rear wheel is properly aligned. If the rear wheel is out of alignment, so is your sprocket. Then the chain would be pulling or tracking to one side of the sprocket/chain. You'd see heavy (relatively) wear on the side of the sprocket teeth. With a properly aligned wheel/sprocket/chain, the lateral forces would be minimal. Whether or not there is a difference in the sizes of the sprocket and chain, the wheel needs to be properly aligned anyway. If not, the same wear potential exists.