My criteria when assessing a bag is .. does it look like a laptop bag?
If the answer is yes, then I pass. I don't think Targus knows how to make a bag without it looking like it's a laptop bag.
I love my Crumpler bags. I've had two; a Base Toucher (for 15" laptops, since passed on to a friend) and a Beer Back for the XPS2. Very well designed and tough too. On the Base Toucher, it's about two to three years old and it doesn't even have a loose thread.
The Booq boa looks a little more 'professional' (aka boring), but at least it doesn't scream "HEY! I GOT A LAPTOP IN ME!" like the Targus bags do.