It really sucks when an away goal decides things but it's also my understanding that not every league has the same style or size pitches... and the atmosphere in different countries is quite different... so there is that to consider... and yeah, it also bring about incentive for attacking play (Damned Italians

).
I'm not the biggest fan of it but I also don't really see any better method... free kicks? A third game at a neutral site? Just add more and more time until someone scores a golden goal?? None of those seem either better, or realistic.