What I took

Since people keep asking what I had in the backpack:

1. 2 pairs of ExOfficio Buzz off pants
2. 3 t-shirts
3. 2 polo shirts
4. 4 pairs of underwear
5. 3 pairs of socks
6. Patagonia Capilene 2 fleece top
   
7. Cabelas Paclite GoreTex jacket
8. First aid kit (bandages, tape, Excedrin, Cipro, Immodium)
9. UV light water purifier
10. 2 books
11. Canon XSi DSLR with a Sigma 18-200 OS zoom
12. iPhone, in ear headphones
    
13. Chargers, replacement batteries, adapter plugs, 2 8gb SD cards
14. Slik sleeping bag liner for the overnight trains
15. Sarong (used as a towel)
16. sunglasses and case
17. 27oz Kleen Kanteen
18. 1 quart zip lock with toiletries (deodorant, sunscreen, shower gel, insect repellent, Braun battery razor, comb, toothbrush, Woolite...)
19. Small flashlight and headlamp (yes...both...I'm paranoid)
20. Copies of all my papers and itineraries
21. Spork
    

And I bought a chain to lock the pack on the trains in India.

The big advantage was the low weight and no checked luggage. The only downside was that I had to explain to every security person in Newark, SFO, and Delhi that YES, THIS IS ALL MY LUGGAGE!!!!

P.S. Yes, Tyler, you can get clothing washed overnight in Indian hotels, so I didn't wear a pair of pants for a week.