I've got a multi-gear bike and while I have nothing against them, I don't get the hype for fixed gears. Having gears makes life much more convenient, and I haven't really experienced any consequences to riding one...
As I said, I don't currently have a fixed gear and there aren't really any consequences to riding a bike with gears. Fixies just give you an absolute purity to the experiance and are great for training things like a smooth pedal stroke.
The bike I ride the most (errands/to class before graduation) is a vintage internal hub 3-speed that I restored. It doesn't have the solid feel of a good fixie but it has the easy maintenance advantage and I don't have to worry about pant legs.