We have a 2005 Yukon XL that we picked up this spring to replace a '02 Caravan. We also looked at Expeditions, Tahoes and Durangos, but the Durango, Tahoe and Expedition didn't have enough room behind the 3rd row seat and the Expedition EL was impossible to find used in our price range (I think the EL came out in 2007?). Ours only had two owners before us (both in the same family) and was in better than excellent condition which made it well worth flying down from NY to Raleigh to pick it up.
It has the 5.3 and the 3.73 rear end, we get 15-16 around town and 18-20 on the highway (depending on speed).
I never thought I would like a GM product, but it rides better than my Volvo does and is as comfortable to sit in.
Aaron Z