roughly 50% of my sales are international. For me, it would be well worth it if I have to stand in line at the post office in order to get correct postage on a package - BUT, if you get yourself a decent scale, you can often avoid even doing that. I buy postage in advance (I go into the post office during a slow period when there's no line), weigh all packages and then affix the proper postage. Voila, no waiting in line.
I don't think that's too burdensome for a significant amount of sales...try it, your milage may vary but it will probably be worth it.