Heavy Shockproof here- been running it for the last 3000 miles and transmission seems to like it. Can't really say it made finding neutral any easier, but shifting was a little quieter than with the Amsoil Severe Gear that was in there before. (I believe it was 75W-90, dealer put it in at 1k svc.) I have an '07 6-speed and the 5th gear whine was slightly less noticeable with the Shockproof than with any other oil. While you could probably tell a difference between Shockproof and 75W-90 gear oil, I doubt the difference would be that great between Shockproof and a 75W-110 or 75W-140 gear oil.
I think one of Shockproof's greatest benefits is the thick film it leaves on everything in the transmission. In one of the HD forums one guy, due to a mistake by his dealer's service tech, ran his transmission for 2500 miles with only an ounce or two of Shockproof in it- and the bike suffered no damage. The heavy film of oil on all the internals kept the transmission lubricated well enough that no damage occurred.
It has been used in Harleys for years and has built a solid reputation as a great gear oil...