non are perfect, and ill probably two, one for travelling, and a smaller one for lighter visits.
I like the laptop compartments, for a laptop or for magazines for holidays.
waterproof cover is essential, either builtin or seperate, i miss a waterbottle holder on my existing bag.
+1 - there is no perfect bag. A testament to that is the fact that I have more camera bags than my wife has purses.
I like my Lowepro Flipside 400 AW as the travel bag - holds plenty of gear (mreco99 - think, room to expand!), although I've pretty much outgrown the possibility of one bag to hold all my gear). It's great for an all-day outing or a multiday trip, but it doesn't get used all that much.
Personally, I've gotten much more use from a more modular system (all Lowepro). I have two Toploader Pro bags, the 65 AW holds body with standard lens (any one of 24-105L, 16-35L, 100L Macro, or others like that), and the 75 AW holds body with white L zoom (70-200/2.8 II or 100-400). The 2x Extender fits in the outer pocket of the 75 AW. I then have a few Lens Cases - a couple of 1W's for 24-105, 16-35, 85L, TS-E 24mm, etc., a 2S for 100L Macro), and a S&F Lens Exchange 200 AW case which holds either white L zoom. Finally, I have the S&F Deluxe Technical Belt, which is basically a sturdy belt with lots of SlipLock attachment loops. This type of setup affords tremendous flexibility. For example, I can attach one lens case to one of the Toploader Pros for any two-lens combination. Or, two lens cases on the belt with the camera over the shoulder for a three-lens walkaround.