First off, this isn't a bad set of brushes considering the price point. The large frame brush is excellent for cleaning debris of your bike. It is soft enough that it won't mar your paint. The loop-shaped brush is strong enough to get moderately stiff debris off your bike and will probably be the one you use the most. The toothbrush-styled one is excellent for difficult debris, as it is very inflexible; it's a good brush for tires.
I haven't found a use for the pipe-cleaner one and am not entirely sure why they included it. Perhaps it would work if you have somewhere where you can't fit the other brushes, such as a small crevice on a mountain bike triangle.
However, there are some problems with this set. First off, while it is hard to see in the picture, for some reason all of the tools hang by their handle on the chain except for the circular brush. It has a hanger on the end, but it isn't a fully enclosed loop--this means it will fall off the chain if you try to rely on this attachment. If you were to hang it on the brush end, you would have to disconnect the chain every time you want to use it, which kind of defeats the point of having the tools connected in a convenient way. The solution is to take a power drill and bore a hole through the handle, which will then let you hang it on the chain.
Second, the brush with the long, stiff bristles that looks like a paintbrush is completely worthless. The first time I used it on the bike bristles started to separate and went falling everywhere. Feel free to give it a try, but you will likely throw it away immediately.