We had a wedding gig a few weeks ago. Typical 6 hour wedding gig, $2500 +$600 sound. Booze, food, cake, always in our agreement. If you want to play weddings almost exclusively, I recommend contracting with an entertainment/booking agency(not for us!) and around here, they get 20% of the gross, but also do marketing of the band. A high quality video of the band performing in front of a large audience that are dancing and clearly having a good time is highly recommended.
Positives: Usually booked far in advance, pretty good money, meet interesting folks, expenses for tax purposes, may get additional wedding/party gigs in the future, who can turn down booze and food in a party atmosphere?
Negatives: may need to learn new/contemporary music constantly although some like it, long commitment for one day(6+ hours?), setting up/sound check while dodging caterers, sometimes obnoxious audience, drunks(band?), requests to lower volume or songs you don't or won't play, may require formal clothing(not for us!), sharing gross with entertainment/booking company.
All I can think of now. Good luck!