I flew into Las Vegas in Sep 2005 ( and May 2004 and Feb 2003 ) with all my camera gear, and I do mean ALL.
A fully kitted LowePro Nature Trekker, and a Peli 1610 "King" case, plus tripod bag, plus suitcase for less important stuff, like clothes
I only took the LF gear in 2005 though, as I didn't have it before then. The customs official at Las Vegas airport said "are you moving here?", cheeky bugger, I wish!.
I tend to put into the LowePro everything I *need* in order to get some photos, like filters, film, main lens, light meter, cable release, DSLR, etc. Enough that I can still take some shots if the Peli went astray, and I take the LowePro as hand luggage. Last time I put the LF camera in the Peli, and would probably do so again, as it's less of a "nickable" item than say a DSLR.
I also had a laptop in the Peli case the first two trips, no problems. Peli case is great, I'd consider getting another, the "carryon" one, to put the LowePro inside or something. If someone was intent on stealing your gear, they wouldn't steal the Peli imho, but something from inside. A Peli is not exactly the kind of thing you can move about covertly
You can lock the case one way, but not the other ( unless you have TSA locks ). I can't remember now which way is which, I think it's outbound from US you can't lock them. That said, you can have someone check them over when you check them in, and then they let you put the locks on. Customs officials are generally quite approachable.
Only trouble I usually have is with the tripod. Checkin staff in the UK tell you to check it in, as it's not big, and a large hollow metal stick with a weighty lump of cast magnesium at one end is not exactly the sort of thing they should allow as carryon... so you check it in, no problem. When you come to bring it back from the USA, they try to charge you extra for the tripod bag, and when you refuse to pay extra to take home the same luggage you brought out for free, they say take it as hand luggage. Just have to explain things simply to them, and they relent eventually.