DavidB will you use the 40D as a backup or as the camera for the 100-400
Both of course!
Mac Book Air is great to travel with if you are a Mac person.
Ugh! One USB port would be painful. I have Firewire/USB drives, as well as USB-only drives with card readers (e.g. Nexto ND2700). In order to make backups it really helps if I can have them all plugged in at once, and the speed of USB is pitiful compared to Firewire. Thus the MacBook Air (with one USB) and the unibody MacBook (with two USB) are really handicapped against the plastic-body MacBooks and the MacBook Pros which have Firewire
and two USBs.
As for tripod, I'm actually taking a big Gitzo CF (in checked luggage of course). Like I said I'm doing another fortnight of non-Antarctic work on the same trip: being limited by a tiny tripod for that would be painful.
Between my travelling companion and myself we're taking in carry-on: MacBook Pro and MacBook, 5DmkII, 40D, G9, LX1, 400D/IR, 17-40, 24-105, 100-400, 50, 85, 580EX, audio recorder, flash cards, about a terabyte of hard disks, along with medicines, iPods, etc. That's all carry-on, in a Crumpler backpack and a normal roller with customised internals. Tripods, clothes, and all the other camera gear goes into roller duffles for check-in.
For years my travel routine has been similar to Michaels: have carry-on bags that fit the size limits of all the airlines you'll be travelling on, and wear clothes with lots of pockets to transfer lenses/etc to temporarily if there are weight issues. Never had a problem yet. Actually, having something like a Domke vest helps streamline going through security scans: easy to take off and put through the scanner, and if you've moved all your keys/etc to it then you don't need to check all your pockets at each checkpoint. And travelling with a partner helps at the checkpoints too: send one person through first and have them collect the bags/etc on the other side in case the other person is delayed in the queue.
