I planted some hairy vetch seed in my backyard a couple years ago. It grew up quickly and it's still coming back. I like the flowers and the organic matter it builds up. It hasn't spread wildly or anything like that for me, but such things can really vary depending on
local conditions.
One thing comes to me, since you're in NC, Scott: For me vetch hasn't done well in the East Tennessee summer. It's something that really likes the southeastern spring and, to a lesser degree, the fall and warmer wintertime. It dies back in summer but grows out again when the temperatures go down.