Have you considered the EMS Boda?
http://www.ems.com/ems-boda-40-conve...0/1305786.html
My father has one and I've used it a number of times and find it to be a great bag. I assumed I would buy an eBags Motherlode if I bought another bag simply because of the lifetime warranty even though I have yet to find any faults with the EMS bag.
But after reading that the shoulder straps on the Motherlode are less than perfect I am not sure I'd buy it.