I think I'm in the same place you are, trying to figure out if I want to drop money on a new geared bike for distance riding. Right now I have a fixed with a particularly long gearing (~88inches, keep in mind florida is a flat state). I'm not in as good of shape as I should be, but if there's a stiff headwind it really makes things difficult. I could shorten up the gear, but then it's going to be hard to keep up with the roadies when we get a tailwind.

In the end I think I'm going to end up getting a geared bike: basically so I know what I'm in for when I embark on a long ride. Adaptability, flexibility. I'll still keep the fixie though, it's just too much fun to ride. Seems like good training too.