I have several different bags depending on what I am doing and how much gear I am taking.
Tamrac Aero Speed 85
http://www.tamrac.com/products/aerospeedpack85/
This is the bag I use most often. Enough room for DSLR, a few lenses, filters, batteries, flash cards, etc. Laptop compartment, room for a little bit of extras (snacks, pistol) and a mesh side pocket.
Negatives- no compartment for water bladder, lens hoods don't fit with lenses, no system for attaching tripod, limited extra storage.
Lowepro Dryzone 200 -
http://store.lowepro.com/dryzone-200
This was my normal carry bag before I bought the Aero. Lots of room in this bag for camera gear, extra gear, tripod attachment, large mesh pockets, waterproof (provided zipper doesn't separate), true waist belt system.
Negatives- pack is HUGE, no water storage of any type, water tight zipper is a PIA when you don't need it and I never really trusted it for total submersion.
Jansport XL Waist Pack (Okay its a Fanny Pack) -
Not actual bag http://www.rockymountaintrail.com/JanSport/Coltrane/TVW0/detail
I use this a lot for short hikes or where I am taking limited gear. The one I have is large enough to hold a DSLR and two L lenses (16-35, 24-105, 70-200) in the main compartment, hold extra battery and memory cards in the smaller zipper bag and I use the water bottle holders to hold my filters and intervalometer. I used two carabiners to mount a shoulder strap so I can use it like a sling bag. If I want it to stay put (like when scaling up or down a hill) I attach the waist belt. With this bag I can also wear a CamelBak for water and non camera extras.
Dueter ACT Liter 65 + 10
http://www.rei.com/product/795605/deuter-act-lite-65-10-pack
This is my new pack for backpacking. I pad the bottom of the bag and then use individual lens cases and/or a combination of the waist pack or small camera bags. I also use this if I know I will be getting wet as I can pack my gear in waterproof bags and place them in this pack. Very comfortable to wear and will hold a lot of gear.
Negative- takes time to setup and put away your camera gear, have to be creative with padding for gear protection, not something you use for every day bag.
So in closing....... like vehicles, guns, and lenses there is no perfect do everything pack.