I think most of the gushing reviewers of this product have been won over by the fantastic properties of granite (a product of mother nature) rather than the properties of this man-made product. Like granite in general, this product will pulverise most spices and herbs.
3 stars could be deemed harsh, but as you probably only want to buy one pestle and mortar for all your needs, I'd say you can do better than buying this one, and here's the reasons why:
It loses one star because the rough part on the pestle should go about half way up the length of it on a well-designed model. Instead, only the crushing tip is rough, meaning you can't use the sides of the pestle to crush against the sides of the mortar - a bit of a shame.
It loses the other star because of size. I made fresh green curry paste in it yesterday, which was great, but I really wish I'd gone for a bigger model as that would have made the job so much easier. I had to mash it in bits, then stir it all together in a bowl, and mash it a bit with the back of a spoon in there to kid myself that I was mashing it together. A larger model would have made the work quicker and easier, and improved the infusion of flavours as I'd be able to work them all together.
I'd advise buying a larger version, unless you have a tiny kitchen, or are too weak to pick up and move a larger set. Even in that case though, you should consider that a larger version will save you a lot of hard work.
Don't worry about cupboard space, a pestle and mortar set is a thing of beauty that should be on display, so as long as there's space on the window sill for a big pestle and mortar, go for that. And try to get one with roughness on the pestle going half-way up, too.