The design is alright. The tablet slots in, then a section of the case folds around underneath it and attaches to the back of the case on the inside with velcro to stop the tablet from sliding out. The only downside of this is that it causes the case to bulge a little in the middle, which is my only real gripe with it. The build quality is decent for the money. The inside of the case is lined with what almost feels like fake suede, so the tablet shouldn't get scratched. When the case is open, the flap can be folded behind the tablet, so it's comfortable to hold and use. The flap is also in 3 sections, so it can be folded into a triangular shape so it functions as a stand, which is a nice idea but it's not that sturdy. Overall, it doesn't add much bulk to the Nexus 7, but it protects it nicely.
There's a cut-out for the front-facing camera and all of the sockets are accessible. There's 5 round holes in the back of the case so that the speaker isn't covered. Because of the shape of the tablet, accessing the power/volume buttons isn't as easy as when the tablet isn't in the case, which is a bit of a pain.
The magnetic lock/unlock thing works great. When you open the case, the screen of the tablet comes on without you having to press the power button, so you can just swipe and unlock it. When you close the case, the screen goes off and the tablet goes to sleep. You can see this in action as it happens once the magnetic gets a certain distance from the edge of the tablet. The magnets also hold the flap of the case closed.
This case is definitely worth a tenner and if that's around what you want to spend then I'd say go for it for sure, but I would happily pay more for one that's a similar design, but better quality. A real leather one - something like the official Amazon leather Kindle case - would be nice.