The first thing I did was to trade the stock 22s on my denali for the Defender LTX m/S2. I think the difference was about $1200 installed. Worth it IMO.
I went with the MIchelin Defenders right off the lot. I didn't want the Bridgestone Alenza that came on the truck as they aren't good in snow or icy conditions, the LTX2s are supposed to be much better in those conditions.
Not sure if my issue is the same but I get a shudder (like rumble strips) when I'm in the 4A mode. If I hit a patch of snow or ice and the road is uphill the truck will shudder. It doesn't shudder all the time but just intermittently and only in the 4A mode.
Personally it would be a deal breaker for me if it was a standard feature. I would not buy the truck. I agree with 2speed it's STOOPID. Replacing that tailgate if you need to will cost a bundle.