I have been there twice - two totaled cars with State Farm. SF is my insurer, but neither claim was my fault (one car was in a wreck where the at-fault driver also had State Farm, and the other was stolen and wrecked).
Both times, when the cars were declared totaled, SF's offer was lower than the cost of a comparable car (same model, same year, same miles, same options, same condition - NOT a new car!). Both times, we said "This is unacceptable" and showed them printed comps (you can get these pretty easily online) to prove it. Both times SF coughed up the full RETAIL value of a comparable car (plus tag and carseat). However, the first time, it took a lot more effort and we had to work our way up the ladder. The second time, we faxed the comps to the adjustor and he said "okay, looks good to me." So be prepared for anything.