For two-strap bags, I find that a sternum strap makes things a lot more comfortable. Waist straps really don't do much.

Chrome makes a really nice line of two-strap bags designed for riding. they're comfy and durable, but pretty expensive. Judging my the fact that my older one is 5 years old and still going, I'd call it worth the money. I just got the backbone, their largest two-strap bag, and like it a lot-- but it's huge.