The bag itself is sturdy. It closes with a zip around the top and also has a flap over the top that closes with a plastic clip. This is great because I can put the camera into the bag and use the clip (but not the zips) to keep the camera secure if I'm out shooting and need fast access to the camera. However, if it's raining you would also need to use the zip.
The bag actually has 2 separators (secured with velcro) inside the main compartment. These seem somewhat redundant as there is no way you will fit more than the camera + lens in this compartment although I have moved me separators close to the bottom of the compartment so that the camera doesn't twist from side-to-side when inside the bag. I can comfortably fit the Nikon D3000 with 18-55mm kit lens inside (lens must be attached to the body). I also have a Nikon AF-S DX Nikkor 55-300mm lens. The camera + 55-300mm lens can fit inside this bag but it is a tight fit. If you use UV filter or something similar the extra couple of millimetres make it a *really* tight fit - but it works.
There is a zip pocket on the front of the bag that can hold the battery charger, mains adapter and the USB lead (it is quite a tight fit). There are two net pockets (one on each size) with a good elastic enclosure. These are great for a place to quickly put the lens-cover and miscellaneous items - but of course they are exposed to the elements. In addition, the underside of the lid has a net pocket (with a zip closer) that is perfect for storing memory cards but nothing much thicker.
The shoulder strap is fully adjustable to any length you like although if you prefer to have it short there is no clip or management for the excess strap - it just hangs there. This is something a couple of elastic bands can fix but if you like to have the bag around waist height this isn't a problem. The top of the bag also has a sturdy carry handle which is for carrying short distances without having to use the shoulder strap.
I've used this bag in really heavy rain and pleased to report that my camera was kept perfectly dry.
5/5 - a really good quality product (at a great price) for just carrying a camera and couple of small accessories.