There's a lot of down time while everyone else takes their turn. You have to set aside one to three hours to play uninterrupted. In real life, you have the benefit of hanging out with these people as you play.
However, I've become a huge fan of http://www.yucata.de/ and http://boardgamearena.com recently and not playing games in real time. Making one or two turns a day means there's no down time, and I can be much more flexible making my move(s) fit into my schedule.