I switched to backpack style bag about 5 years ago, and would never go back. Having another hand free while traversing airports makes a world of difference.

The bag I have is a Targus, black nylon. Has held up extremely well after 5 years of average 1.5 weeks per month on the road, looks practically new when I vacuum it up.

The main feature my bag doesn't have that I would like is stowable straps. As a consultant for a software company, most of the time I get by with business casual attire, but on those rare "suit occasions", I would rather stow the straps and just carry it by the handle.

The other main problem is that I just got a new, larger screen laptop, and it is a tight squeeze, so I will probably replace it when I see something else I like, but I haven't been really actively searching.