I thought it was very important when buying our first travel system, so we got one where we could switch the seat almost at a click of a button (although DH was rather taken with the Mothercare Spin, which is literally at the swivel of the handle, although I couldn't see the point of that). I loved the fact that I could see my DD at all times.
However, at about 9 or 10mths, she,started craning around the hood & trying to see where she's going, so we switched it. It isn't recommended/safety approved, but we switched it easily enough with her in it and found that really handy (think blizzard going into the hood etc). Sometimes I would like her parent facing even at 2.3yo just so I can hear her properly & talk about what we're doing, but I think she prefers seeing where we're going.
Now I'm buying a double/tandem, I really want the newborn seat/carrycot parent facing, just so I know whether they're ok etc. Maybe it isn't essential all the time, but for me, its an important factor.