Well, what can I say? It does what it says on the tub, and comes with a die and whole bunch of rules for various games you can play, some of which were completely new to me.
Now - I do have to state that I did not buy these as a toy to play with, but to use as a subject to be used in a photo shoot and to that end they fit the bill perfectly. Also, I wasn't so miserable to bother counting them (someone noted that less than 50 were in the tub), but there seems to be quite a lot, and you could give them to the kids who may go on to win or lose some more.
Anyhow, how do I rate this product - well, when I was a kid I used to love playing marbles, so to me, they're lots of fun. Plus marbles involves counting, which I guess means it is educational. How durable are they? Well they are chunky spheres of glass, which would be pretty difficult to damage. Ultimately, no complaints from me - they're marble-ous!