I have a bag fetish - there I said it. Tried so many different style and designs and never really hit on the right one.
I think there's a bit of an overall style choices to make - do you want one that is very techy or 'back pack-y' looking, do you want a ton of organization/compartments, or would you prefer versatility in packing it?
I could not be happier with the Peak Design Travel Backpack (45L) The straps are quite comfortable when it is loaded to the max (and there's even a hide-away waist belt, though I've never used it). It's fairly minimalist looking on the outside, and basically only two main compartments, one with a few smaller zippered areas. The rest is one big cavity which for me adds to the versatility. There is a dedicated laptop sleeve.
I've filled this thing with cameras, lenses and electronics (using their own equally excellent tech and toiletries bags), I've filled it with my cycling helmet, shoes and gear, or with my ski helmet and gear, I've used it for work trips and love that it doesn't look like my hiking bags.
Love that there are so many ways to get in the bag with zips on the side and a back clamshell - the latter is great because you lay it down on the outside and open from the portion that is against your back, great for getting your camera gear out and preventing you from getting mud on the part that will touch your body (or digging through it at an airport in nowhere India where whatever on the floor is also questionable).
They definitely make a lot of stuff geared for photographers, but this is just a great bag in general. Also love all the grab straps at the top, bottom and back of it as it makes it easy to grab and go without even putting it on your back. Bonus bag trolley sleeve as well.
Pricey but seriously well thought out with a high quality of build.
Ode to my Peak Design bag...