The national average of air traffic controller errors is 1 in 84,000 "flight operations." New York City area folks make 1 in 40,000. If the worst that happens from these errors is that your plane goes for a swim in the Hudson, I'd say they're not too severe. Also, that wasn't an error (I don't think), right? [NYPost]
If you have an iOS device, jump on the App Store and get "LiveATC". Then bring up the live audio stream for JFK Tower. Listen to it for just five minutes. Then you'll be amazed at how they manage it all without a lot more errors.
NY airspace is as complicated as it gets. JFK and the other NY airports deal with a huge amount of congestion. There's a reason why I listen to that stream over the others in the app. It's more exciting!