I commute (by bus, train and foot) and it takes me about 2h45 for the round trip - a fairly big change from the 25min round trip (walking) I was doing until 6months ago! If I could drive it would be a 1h30 max round trip.
As I can't drive it's difficult for me to answer the question but in general I wouldn't want to spend more than 3hrs a day commuting unless it was a job I enjoyed and/or paid extremely well. I'm pretty much at my limit now as it means including travel time and lunch break I'm doing a 56hr week as standard.
One advantage of travelling by car is that aside from being stuck in traffic, there is no 'wasted time'. It's door to door so even if you are crawling along in places you are still making quicker time than someone sat on a station platform, and there's rarely much walking at either end. Generally speaking it also means that if you set off 5mins late, you will get to work 5mins late. Compare to public transport where if you miss a bus or train by only a couple of mins, you can end up being 30mins+ late to work.