The bug was first collected in Allentown, PA in 1998 and made it's way into the Hudson Valley of New York by 2008. It's spreading throughout North America.
While harmless to humans, it can congregate in large numbers to overwinter in homes and other structures and is an agricultural pest damaging crops such as apples and corn (both important in the Hudson Valley).
While it can be confused with some other species of native shield bugs, the key identifying feature are the white bands on the antennae and the alternating light and dark bands on the abdominal segments which protrude beneath their wings (both features seen in picture at right).
And yes, they do stink -- especially if you crush them (if I find any, I will crush and smell them since I never have -- I'm strange like that).
If you see any in the Hudson Valley, the Cornell Cooperative Extension would like you to catch them and send them in with some data on where they were found. Read here for details. I've got my kids on it - if any are in our yard this year, they'll find them!
Apple and corn damaged by marmorated stinkbugs