I am about to insult this museum, but I have a few caveats. First, if you're taking children to D.C., this is an okay museum – it’s not nearly as good as the outdoor sculpture garden (by the National Gallery) or the Air and Space Museum, but it does attempt to aim some exhibits at kids. Second, the museum is near Union Station, so if you only have 5 minutes to see a museum before your train, you might come here.
Now for my review: Unless you really love stamps or have some burning desire to visit a postal store in the nation's capitol, there are only two reasons to visit this museum:
1) Go with friends for a comedic exploration of how you create an entire museum from a letter and a stamp. The creativity is amazing.
2) Go by yourself on a hot day because you are near Union Station and need a public restroom or a building with air-conditioning.