Pursuant to the discussion of chain wear measuring tools...
I found the Shimano tool on sale and picked it up, as it's in theory more accurate.
Below are images of...
1) the Shimano tool on a chain that appears to be worn out
2) the Park Tools checker on the same chain (at the same place)
3) the Spin Doctor tool, same place, 0.75% side
4) the Spin Doctor tool, same place, 1.0% side.
It looks like the Park Tools and Spin Doctor checkers agree with the Shimano tool at about the 0.75% mark.
Steve