I saw it mentioned by a member in one of the forums that the Delens-ing increased throw by 13% and increased lumens by 14% (my calculations from his numbers). While I was willing to wait for more information, from an optical standpoint, borosilicate glass in that thickness should only see an 6-8% loss in transmission loss and that's making the assumption it's borosilicate. In any case, I think those gains are overly optimistic and should be more thoroughly tested. When Vinh posted more conservative numbers which make a lot more sense.
With regards to tint shift, it's unlikely that a single, optically coated window is causing significant levels of shift and more likely that it's just the LED and the current level at which it's being driven, or the tint lotteries which we know happen. Perhaps latter versions of the SBT90 will shift less at different currents. I'm guessing that if Vinh tested the same light with and without the window, both would show nearly identical tint. This LED doesn't have any green when it's being driven hard.
Someone measured an output increase of 9.8% after removing the LED lens in a different light.