The LowePro 350 is a great bag in terms of quality of finish (no loose threads, zips work well, padding is firm, velcro in good places, etc). There are some compromises of course, which is the nature of the design.
This system is designed to carry a laptop and camera gear, plus a reasonable "loose" section for drinks/food/etc at the top. I bought this for a holiday trip to the West Coast of Scotland which I knew would involve quite a bit of walking. I also knew I would NOT be carrying the laptop on the walks! It was a good method of getting the laptop to the accommodation fully protected without having to add yet another bag to the already full car. I also use it for walking to the office when at work, where it fits my use very well.
The downside of the 350 is that it doesn't have an integrated method of carrying a tripod - you'd fit a gorillapod in the top, or maybe a compact monopod, but my venerable 20-year old Velbon had to stay at home! A separate carrying method might be fixed on, as the bag has a flat bottom, so the tripod could be slung underneath if you're clever with your bungee's.
Also, there's no dedicated rain cover, so any showers or heavier rain would see you ducking for cover. The main camera compartment zips are covered by an extra flap, so this should provide reasonable protection, but the side zip used to access the camera body remain exposed. Driving rain might make it through that eventually.
In use on the walks the bag is _very_ comfortable. My kit (so far) consists of: Canon 40D, 10-22mm EFS USM, 17-85mm EFS USM IS, 70-200mm EF L USM IS (f4), weighing in at approximately 3kg altogether. I normally walked with the body and lens in hand (strap round neck just in case).
The adjustability of the shoulder harness and waist supports are excellent and I was able to easily switch between shoulder and waist for primary load bearing when required. A bit more venting at the back would be useful though, as it gets quite hot on longer or brisker walks. I didn't really find the side-access feature all that useful, though I did use it. I would frequently need to fully un-shoulder the bag to switch lenses, for example.
Inside the padded camera section, you have adjustable panels. The range of adjustment is reasonable but not infinite - the stick patches are in set areas. With the lens hood for the wide angle 10-22mm lens in one "cell", you'd still have room for a flash or fourth lens, assuming the longer lens remains attached to the camera body. You could put the hoods (for any lens they don't conveniently reverse-fit) into the top compartment and have room for a fifth lens (if you needed it), or four lenses plus a flash unit. Really depends on what you've got though.
I was able to fit two OS Explorer maps in the exterior mesh pocket, along with a 350ml water bottle. The top compartment happily took my 500ml flask, spare battery, lunch box (holding two rolls) and meusli snack bars, etc, with a little spare room left over.
Overall, I'd say this is an excellent "urban" backpack for those wanting to carry a laptop as well as camera regularly. It gets to be quite heavy if fully loaded, depending on your laptop specs. Mine's a Vaio weighing in at 3kg without the power brick, so adds quite a bit, but I can get all the power adapter/chargers and various cables in the top, so long as I don't want to carry anything else!
For fully "wild" use, I'd perhaps recommend looking further, particularly if you need to add a tripod to your carried kit, but you won't be dissappointed with the quality of this bag.