It's an interesting question. If Project Vigilant had compromised Tor, I'd expect there to be quite a few pedophiles who had used it to share cp getting busted. I'm not aware of any such incidents, let alone many. I imagine that the government wouldn't want to give away that they had it compromised, and so would simply use the information to compose a list of people to watch for slip ups, but one would expect to see a rise in the number of arrests, which would likely get at least some play in the MSM.
Conversely, if the NSA had compromised it one would expect to see no outward signs, as they a) don't care about pedophiles, b) would claim "national security" to hide the means of tracking terror suspects from the public's eye, and c) likely wouldn't tell anyone when they did apprehend someone.
I think it's probably pretty likely that the NSA is running a few nodes, but that's the risk you take wit something like Tor, just as bittorrent seeders risk riaa proxies downloading from them.