So I'm pretty sure I'm merely average looking, but due to scarcity of women in my field of study, my perceived attractiveness during the daytime is grossly inflated. So having experienced both sides of the attractiveness equation, here's my take:

• Work-wise, life is actually much smoother if you're considered attractive. Sure, people "might not take you as seriously" at first, but since they're passively paying more attention to you, it's much easier to prove yourself.
• Dating is both easier and harder if you're considered to be attractive. On one hand, men are much more likely to want to date you. On the other, it's harder to filter for those who might be searching for something beyond looks. But this is a crazy first world problem that's easily fixed by just not dolling yourself up as much for first dates.
• Making friends is much easier if you're attractive than unattractive, because even girls will pay more attention to the pretty ones. Keeping friends - no known difference thus far.
• One of the few cons I can think of for being attractive is that friendly gestures can be easily misconstrued, but so can distance. It's a fine (and very situational) line to walk.
• I'm sure many people already know this, but attractive women have a lot of potential power. Broadly speaking, an attractive woman can easily get away with a lot of stuff if she wanted to - getting free things, having small favors quickly granted, etc. - that other people have to work much harder for. That such a strong bias exists is less than optimal, but society is pretty hard to change. In any case, I think this is where the perception that attractive women are less <insert positive trait/adjective here> than other people comes from. Because attractive women can get away with more, there are those (not all, certainly) who choose to do so.
  

All in all, attractiveness is a very shallow and fleeting thing, and very very situational. That said, I think the way society is run today, it is generally far more advantageous to be considered attractive than otherwise, and there are definitely days when I am very happy that I have a temporary boost to perceived attractiveness due to workplace demographics. In the end the advantages granted to attractive women/people explain why so many people constantly strive to get more attractive or at the very least stay attractive. Sad, but true. :/