Best: ceremony and reception at the same place, with drinks and nibblies and games for an hour or so in between. Something close to public transport and accommodation (sometimes a remote venue far, far away sounds great but can be a real challenge for guests to get to and arrange accommodation), short speeches done early on, perhaps while entree is served, get all the formalities over quickly, great music and lots of dancing.
Worst: remote venue, too structured eg: formal sit down, loads of long speeches, awful 'wedding food' (restaurants can be better venues and the food better!).
Cocktail-style functions seem to be the go at the moment- lots and lots of yummy finger food, with casual seating and a ceremony on the lawn/ beach/ deck beforehand- this style of wedding is always fun and I have found they create a great 'vibe', whether it be on a farm, in a backyard, at a restaurant or at a nice wedding venue.