There are plenty of laptop bags out there, some of them incredibly expensive with every conceivable customised pocket imaginable and enough padding to protect against a truck. This bag isn't one of them but it gets the job done and for the price, is quite decent. You can easily add a little padding yourself when you pack it to ease concerns and as long as you don't assume your laptop is invulnerable and remain relatively cautious, it should be fine.
What there is:
There are three compartments to the bag. The main compartment contains a pocket for your laptop which can be secured with an elasticated velcro strap. The pocket is attached to the back of the bag so that the laptop will be closest to your body when the bag is worn and so doesn't threaten to throw you off balance. The pocket also suspends the laptop so that should the bag be placed on the floor on its base, no part of the laptop SHOULD come into contact with the floor. There is ample room in the rest of the main compartment for things such as books, files, cables etc.
There is a small compartment at the front of the bag which contains a mesh pocket and a few elasticated loops for pens. There's a small padded pocket on one side of the bag, and a mesh pocket on the other side. The bag also comes with a small mobile phone case attached to one of the straps. It can easily be removed (velcro).
How good is it:
I use this with a 15" unibody Macbook Pro and inside a second skin, my laptop fits in the pocket in the main compartment well. Initially I was concerned the velcro securing strap at the top of the pocket would allow my laptop to move around too much but it actually holds it in place fairly tightly. It still would have been nice to see a bit more velcro on the strap to allow bigger or smaller laptops to be secured just as tightly. Ideally there should also be a padded flap at the top of the pocket to give the top end of the laptop a little protection. A lack of padding is the main problem inside the bag. The pocket is padded a little (though not much) and without a second skin, the part of my laptop poking out of the top of the pocket would have very little protection at all. Due to this I feel the need to add padding of my own when I use it (over the top of the pocket, under the pocket and wrapping up anything pointy in the main compartment like the plug!). Of course you could argue that there's no point in buying this bag if you have to add your own padding but if you really value your laptop, I'd think you'd add padding or take care packing it even in a hugely expensive purpose built bag.
The pocket on the front is big enough to carry quite a few accessories though there isn't really any padding at all. The mesh pocket lets you keep smaller things separate and easy to spot while I found the pen holder loops really quite handy for memory sticks. The padded pocket on the side is good for carrying a non-bulky power adapter or a mouse while the mobile holder could also be used for a small camera if you wanted and is handily removable.
Overall:
The bag is quite neat and has the advantage of not looking like it might contain anything hugely valuable, it certainly doesn't look like a laptop bag. The main compartment zips closed using two zippers which I secure with a small screwgate karabiner for extra safety.
Basically this is a cheap bag. You can definitely get better but you'll have to pay for it and if you use your common sense when packing and carrying this bag, you can keep your laptop just as safe if not safer than if you put it in a bag costing hundreds.