I dated two girls at once for approximately 2 weeks, and I hated it.
Got set up by 2 different friends(that don't even know each other) with a new girl just 1 day apart. Met one on a Friday night, the other on a Saturday. Liked them both a lot. Went out with each again during the next week on different weeknights, again the following weekend(Fri/Sat) and then while making more plans with both(both wanted to do something on the following Saturday) I had to call it quits with one. It was actually a damn hard decision as I liked them both, but for different reasons. One was younger, perky, cute, fun, great in bed, but still living at home and not really too established yet in her career(was working retail while going to college part time), the other was a couple years older than me, cute, a little more laid back and relaxed, but hadn't slept with her yet, and more established in her life(good career, owned a home, etc).
I chose the older one, cut it off with the younger one, and 2 years later was married to the older one and now we have a kid together, so it seems as though I made the right choice.
All of this was after coming off a bad relationship and not really dating anyone for like a year and a half. Its odd how nothing happens for so long, but then when it rains, it pours. Wish I could have met the younger one a year earlier and had some time to have more fun with her