Obviously a great .us name. I wouldn't even think about selling it now. It is almost sure to appreciate significantly in value over the next few years as buyers become more familiar with .us.
That's what I figured. For an appraisal, then, I will simply say that the ".US" extension, at this time, is simply too much in its infancy to draw any concrete conclusions. However, in my opinion, if one were to speculate in such extensions, then one could do a lot worse than this domain. Hope that helps. Good Luck.
If you want a $ value today I think Dr. Who is on the right track - $500 to $1K. Could be 10 times that in 5 years. Keep it. No gaurantees of course, but where else are you likely to get a 1000% appreciation over today's value in a 5 year period?