I started with a Lowepro Nova 4. Now I use a Lowepro Slingshot 200 AW. It is starting to get a bit cramped, and sometimes it is uncomfortable/unwieldy. I've been looking at the Lowepro Fastpacks which are a backpack version of the Slingshot. They look more comfortable, but I'm not sure they would have much more room. There will never be a "perfect" bag though.
