Extremely reliable! I'm not sure about the older models (they were redone for the model year 2007), but I have a 2009. It is my wife's car and I was in an accident in it while picking my children up from school one day. Thankfully they were not in the vehicle, but I have no doubt that it saved my life. I hit a vehicle that is known for its reputation, that vehicle wasn't able to drive away while the Tahoe had just a little bump. Of course there was a lot of damage that wasn't seen which ended up costing the other driver's insurance company a pretty penny. I feel a lot safer in it since this happened as I was weary at first. I feel a lot better about my wife and children riding in it.
As for any other issues, we haven't experience any yet. I would assume that the older models wouldn't either considering that they are tried and true.
