Although Meetro is the first location-aware instant messaging service that I know of, I can't see it taking off. My issues with it are two fold; I have to create a whole new identity to use the service, and if I want to know where my friends are, I have to get them to do the same. Although the interface of the program has come a long way from when I first saw it in its early beta stages, its still not nearly as user friendly or intuitive as I would like. Ideally, I'd like to see a plug-in for iChat or Adium which allows me to see the location of my regular AIM/MSNIM/YIM buddies when I mouse over them.
In any case, Meetro is certainly an interesting concept, and worth checking out, even if only to get a taste of what surely will be many similar services to come.