My experience always mirrored Paul's ... timed my CH exit to the announcements, and never really had any line to speak of at the TSA check, so lack of a proper priority lane has never been an issue. Because of the later departure of the LHR flights, and with VS usually staggered a bit between the two BA flights, I can't remember ever having more than 10 folks in the area before the glass doors. There's usually a few in line after the glass, but they move quickly unless you do in fact have an individual whose attire or gear is not in line with the rules.
FWIW, my experience of priority lanes is widely varied between different US facilities. A few have a fully separate security line unless it's a hub - like UA domestic at SFO. Many more have a short cut of sorts akin to Paul's queue jumping chit concept at SFO, but on a large scale this can be nightmarish. UA at DEN is a zoo sometimes, as you do have a separate line for document check, but then you really are back in the mixer for screening lines, at times things tending to get a little out of hand.
At some places you can access priority lanes through status, other places reserve this perk to golds or higher only. I've never found it terribly easy to understand. Went through LAX on UA in late July, and it was an absolute mess early morning, with tons of people lining up to catch east coast and Hawaii flights, and the place completely disorganized, people shifting back and forth between different lines. ORD International Terminal also comes to mind as a paragon of disorganization.
I've never anywhere seen anything in Europe or the US for biz class passengers remotely like VS's LHR UC/Gold security channel (international First Class do get special attention in some places, of course). In general, I can't think of a lot of places where priority will make a significant difference, except maybe for JFK. My experience of US security is that it will work reasonably well, or not, depending on how well terminals are designed to deal with it (most being designed prior to 9/11 style security requirements).
UA themselves are inconsistent in how they choose to deal with premium passengers abroad. At LHR T1, you get to use the preferred channel only as F, C or GS - even 1Ks (with 1K prominently printed on their BP) have to take the regular security route if they're in Y. There's a lot of variables to this, a lot of different costs, no doubt, and it just changes all over. So I don't think it's as easy as 'print your status and you get preferential treatment'.
