On the hunt for the perfect travel backback

I travel a lot. When I travel there is mostly a flight and one or more overnight stays involved. So far I was using a Tumi backpack, which served me well. After 10 years of service it is showing its age and I'm looking to retire it. Turns out the hunt for a replacement is far more difficult than I expected. I'm looking for the ultimate backpack for the frequent traveller. I thought my criteria are not uncommon:

• Robust and torture resistant: I carry heavy loads and long distances (mostly running to gates to catch that flight) and don't need a strap coming off. It also shouldn't look -after a month of use- worn out like 19th century gold digger equipment.
• Fit under an airline seat (which is kind of a contradiction to the amount of stuff I need to carry
• Carry the corporate Lenovo T61 (no Macbook anytime soon) and its little brother
• Well organized space for: 2 power supplies, 2 international adapters, various cables, business cards, phone, passport, wallet for second currency, tickets, external disks, iPod etc.
• Carry a folder with reference materials (and the bill collection) and a book
• Have space for shirt, underwear and toothbrush (many trips are overnight)
• Umbrella -- best outside so it doesn't soak the stuff inside after use
• Ability to be locked
• Needs to offer service/warranty in Singapore (I can buy it anywhere)
• I like black, but that's optional
• Needs to be sold in a place I can have a look (means: any airport/city in AP). Singapore would be an advantage

Meet the contestants, the first two come from the luggage industry, the later a backback experts:

• The incumbent brand sends its model Alpha T-pass Business Class Briefpack:
  
  Having a track record and an excellent customer service is clearly and advantage. Tumi is in the upper price quadrant.
• Samsonite offers the Pro-DXL2 Laptop backpack
  
  The Samsonite offers a dedicated garment compartment that even features a hanger for a jacket.
• Booq sends in 2 models which I quite liked and examined yesterday: the BOA3M and the Phython XM:
  
  
  Problem with both of them: Since Booq has no luggage heritage they don't feature zips that can be locked. A big disadvantage for international travel.
• Timbuk2 Patrol
  
  The website states it is sold in Singapore, but I haven't found a shop yet.
• Others (seen online, but haven't touched them yet): Spire Meta, Megalopolis Aero, Brain Bag and Wenger's Swiss Gear

On the hunt I came across a number of interesting looking messenger bags too. Should I challenge my assumption that a backpack is best for my needs? What's your take? Backpack yes/no and what model to pick?
Update (14 July 2009): A new contestant entered the race which looks like a good compromize:

Travelpro executive first backpack. It features 9 externally accessibe compartments, 2 of them lockable, plenty of storage space and TravelPro's sturdy ballistic nylon. I already have one of their products and was quite happy, so I'll go with that for now.