First time I've ever been on a flight that made the news:
As I posted to the FlyerTalk US Airways forum section, I was of course sitting up front (with two empty seats next to me, which was a real blessing given the delay) and someone in the far aisle seat). We really didn't see or hear anything. The flight seemed to be entirely normal until I felt the dip for landing at 23:00 and thought that was odd - and then the pilot announced we were making a "precautionary landing" at BOS and then would have a bunch of paperwork to file. He went on to say that the problem was nothing to do with flight operations but they didn't want to have to be dealing with it over the North Atlantic. We landed about 23:15, and I remember thinking that it would be at least two hours, since that seems to be the average turnaround time for these things. Pilot eventually said the problem was an "uncooperative passenger" who needed to be removed from the plane.
And we still didn't really see anything except a few people walking up the aisles. I certainly didn't see anyone obviously handcuffed or anything or anyone who was obviously police. (People sitting in the back, who would have seen more, aren't likely to read Flyertalk!) After about an hour they announced that the *other* thing that was going to take time was figuring out which were his bags and extracting them from the hold, since obviously they couldn't fly with his unaccompanied baggage. And then we eventually took off again around 1:15. Didn't land until 12:15 UK time - I think we may have been held at LHR for about half an hour.
On the tube going home I ran into a BA first officer and asked him what he thought had happened, and he guessed perhaps a drunk and aggressive passenger - he said anxious flyers sometimes have a few too many before they get on the plane, or take valium which, when mixed with alcohol, can make them quite aggressive. I told him about a friend of mine in the 1970s who after a somewhat stressful tour in the US let loose on the plane home and got so drunk the crew locked him in the lavatory (he never even went through customs and immigration when they landed; they waited until everyone else was off the plane and then shoved him, shouting that he wanted to see the pilot, through a side door into his wife's arms). "Yeah," he said, "we're not allowed to do that now."
As an aside: the plane we were on is US's brand new Airbus 330. I think my flight out to the US was one of its first flights if not its first flight. Unlike the other planes of recent years, this one is very, very cold, especially on the delayed flight. The crew told me they did everything they could - and occasionally you could feel a burst of the temp going up, but it never stayed up. Some other points: the plane has trays the full width of the seat, which is much better, and the underseat space is pretty good. There's a widescreen LCD display in the back of each seat, and all the controls, both for the in-flight entertainment and for lighting and calling stewards, are under the screen, so the armrests are blank except for a headphone jack (standard, no more two-prong stuff). I believe the crew are dealing with some inconveniences in the galleys until they get used to it. The food on this last trip was god-awful, but I don't think the plane had anything to do with that. It's noticeable that there's a lot more bright white LED lighting than on previous planes. The one real thing most people probably won't like is that the seats are probably a little narrower. The one real thing *I* don't like is: no power outlets for laptop in economy, the reason I started flying US in the first place. It's a real retrograde step.