We acquired a whole bunch of Lego for my son's 7th birthday, one of the boxes being the Lego 6117 Wheels Set.
We also purchased some bricks from the Lego Pick-A-Brick section of the Lego shop, to complement these wheels, e.g. a mini figure, lots of car windscreens, steering wheels and various plate bricks to name a few. Then it's down to my son's imagination to build various vehicles.
There's plenty of variety of wheels in the 6118 set and enough of each type to make suitable vehicles. All-in-all, I'd give this box set about 7 out of 10.