Gothamist,
I didn't say driveshaft angularity, I said driveaxle angularity. There is a difference. And yes, I know about Ian's experience.
Driveaxle angularity can cause vibration as well as excessive CV Joint wear. After reading Ian's write-up on the SLR suspension and the problem he had with a slight vibration with the hubs engaged, I believe I know why it occurs. Although this is speculation, it is based on years of doing vibration diagnosis at automotive dealerships. I am willing to bet the vibration is coming from the reduced bushing size between the frame mount and the differential.
If you will notice in the GM IFS lift kits, the entire diff and mounting assembly is dropped. In the SLR kit is dropped by removing the centered mounting bushing and installing an off-center mounting bushing. This puts the diff closer to the frame. The less rubber between the frame and diff, the more vibration will be transferred during operation of the diff. Since all gear parts move with the hubs locked, this will occur whether in 4WD or not. But the reduced driveaxle angle is far superior than some of the angles I have seen in other lift kits.
As for the "serious off-roading" comment you made, I agree. But I consider the off-roading I do serious, albeit with limitations. I want my truck to be the best it can be for what I use it for. I know I won't ever crush cars with it, but I do need it to get me through heavy snow, sand and mud if needed.