Just had the 2" factory lift installed on my 20 Sierra Elevation, part number 84993582. Got the kit for $980 on sale from GM Partsexperts and got it installed for $513 + tax ($408 for the install and $105 for the wheel alignment) at my local GM dealer. For some reason they were cheap compared to other dealers I called who were quoting between $800 and $750. They did all the calibration and computer updates. The only thing I wish they included was the headlight adjustment but that's easy enough to do myself.
I love it, looks just like an AT4 from the outside, high enough to look more aggressive but not outrageous. Ride is comfortable, a little stiffer but may just need to settle. Factory warranty is still intact and I kept the old parts JUST in case I want it back to factory.