I ride with a windshield. I have ridden without, but I think the advantages of having one outweigh the the disadvantages. A few have mentioned that they don't like looking through a dirty windshield, but at the same time, if you didn't have the windshield on, all those bugs, birds, thrown grovel and such would be hitting you in the chest. I was coming home one night around sun down, and it must have been hatching night for all those little gnats or something. By the time I got home, my skin was almost black with bugs. I've also taken one too many june bugs shots to the neck. Bee swarms... wasps... yeah, my windshield stays on.
Bugs aside, I should mention that I generally do 200-300 mile rides every other weekend or so. The relief from the wind just makes the ride more comfortable and less tiring.
Many people don't like the look of a windshield. I think if you get the right shield for the bike, it could actually make it look better, but that's just my opinion.