When I installed L6 beta 15 and each RC thereafter, my Logos icon was unaffected. I was thrilled that finally the dreaded app icon bug was fixed. But no, it's not. Now both the Start menu icon and the Taskbar icon are back to generic Windows app icons. 
I believe this happened with the update to L6 gold (6.0.0.3700; not sure precisely when this happened, because it hadn't happened yet as of RC3 which I thought was identical to gold, but it's definitely there today; I had another app update today after the massive resource update, and I think that's when it happened. I thought beta testers didn't get another app update once a release candidate goes gold, but I might be mistaken.).
