Standbuck
My experience would echo Sikamalc's. At one time I was travelling to and from the States 6 or 8 times a year - and this post 9/11. There were some things I couldn't get in hand luggage (the high seat, the shooting bench, the turret press and the deer tripod would have been a bit of a squeeze) but I've brought plenty back before.
In the past I've taken optics in my hand luggage on the basis that (a) they are delicate items, and (b) I can then declare them in the UK. The Leupold scopes typically worked out less than the personal duty free allowance. These days I would tend to put them in checked in baggage if I had any, which isn't very often. I would always check in any knives, riflestocks, reloading kit, etc.
I have always found that if you treat the security people curteously then they are pleasant and friendly....and often just interested in hunting outside the US. I've swapped a few good stories with them and had reccomendations of hunting camps and fishing holes!
willie_gunn