Another vote for the Farpoint 40. I've taken mine all over SE Asia, western Europe, Mexico and the US. It's not a perfect bag, but given availability, price and warranty I haven't found anything that beats it (yet).
edit: worth noting this isn't waterproof and I don't believe it's water resistant. I've found that if I'm worried about something getting wet I'll wrap it in heavy duty plastic bag and place it inside the bag. The bag is fairly sturdy, so I wouldn't worry about punctures/rips. This will fit as a carry on on nearly any wide body aircraft. The only time fit has been questionable is with smaller regional jets and turbo props, but I've still managed to shove it under my seat without issue.