The auto box requires an oil change if it's to last.
Volvo say the gearbox oil doesn't need changing but there's hundreds of threads out there discussing this and showing the state of the gear oil.
Burnt oil will cause poor shifting and drastically shorten the life of the 'box.
Check the oil, it should be a nice light red. If it's dark or smells burnt then it needs changing.
If the car has been towing, ask for proof the gear oil has been changed, if it hasn't be very careful, the box could well be trashed at less than 50k miles...
If you buying a used auto then I'd change the gear oil immediately and then again after about 10k miles. 30-50k thereafter depending on what you're doing with it.
Towing regularly? - 20k and think about an extra oil cooler.
Couple of threads, well worth a read
http://www.volvoxc.com/forums/showthread.php?t=12169
http://www.volvoxc.com/forums/showthread.php?t=15297
Manual cars are a different beast and have their own special, and expensive, problems. At least the gearbox is bit tougher...
Saying that, I did have the gear oil changed at 20k and am having it done again at ~70k on the next service just to be sure