Pros: Cheap. A repair set sold locally for about the same price only contains four rubber patches. This one contains 48!
Build quality seems good, then again, there's not much that could go wrong with rubber patches.
They have a good thickness, but are not too stiff.

Cons: Sets bought locally usually contain a bit of sandpaper to prepare the tire before glueing. No biggie though, sandpaper isn't exactly expensive.
Instructions are only in Chineese. If you don't know how to use it, print out some instructions from the internet in advance.
The glue just comes in one big tube. Would be better to have several smaller ones.

Other Thoughts: I bought it as a refill for my bike tools. Perfect for it.
The cardboard box isn't perfect to keep on your bike, and is too big anyways. Just take a few patches with you, keep the rest at home.
Still hope you'll never need it.

Bottomline: Buy if you have a bike ;)
Just one package will be enough for you, your family, and your friends for quite a long time.