I have 3 Lowepro products, I like them the most as far as dedicated camera gear.
First item that I have is a Nova (170AW) - which fits one body with lens attached and a lens next to it. It is an over the shoulder design, and handy for 'shorter days' with little walking- but not suitable for 'treks' / multi-day or long shooting days.
Then I bought a Lowepro Slingshot 300AW, which could definitely carry more gear (eg one body and all my 5 lenses, or 2 bodies less a lens or two). It is fairly convenient to access items (via a 'sling' motion - and a flap can then be opened). But I found out it is not the most comfortable for long periods with that weight unbalanced (as it only has 1 diagonal strap, it feels 'lob-sided').
So because I do a lot of walking, I wanted something that suited me better. In stores I had tried many other brands and sizes - but kept going back to the Lowepro Fastpack 350
Therefore I purchased the Lowepro Fastpack 350, which is somewhat of a similar design - except it has 2 straps, and a few other small differences, and is definitely MUCH better for long walks. It (like the Slingshot 300) has a handy top accessories compartment, which can be used for 'that extra lens' - or lunch, or a thin jacket, etc.
So for what you need, I would recommend the Lowepro Fastpack 350 (I generally don't take my laptop with me in it, but it can work well). PS I have kept the Slingshot 300 as my 'at home storage'.
Edit: my gear includes: Canon 7D body, Canon 350D body, Canon 15-85mm lens, Canon 70-300mm L, Canon 100mm macro, Sigma 8-16mm, Canon 18-55mm and Nissin 866 mkII flash.
Only thing is that none of my Lowepro bags have a place to store a tripod... but I usually carry that by hand, or 'tie' it to my bag...