I purchased a set of the hematite dice for one of my friends as a gift last year, and another gamer in our group also has a set of Dwarven Stones. There's no question that they're very cool in theory...but not so much in practice.
Here are the problems as I see them:
1) They're way too small.
2) They are very irregular in shape, which leads to skewed rolling.
3) From what I've been told by a few people in the dice manufacture industry, the Stones have a tendency to fracture along unseen faults. That flat out
SUCKS when you consider that they cost $25 and up IIRC.
4) Because of the aforementioned issues, you'll likely find yourself using them quite sparingly...which sorta mitigates owning them IMO.
If you do decide to proceed with your purchase, inspect the dice
very carefully before leaving the store -- unless your ordering them online. In that case, cross your fingers and pray for a good set. Once you've got them, make certain that you
always roll them on a forgiving surface like a mouse pad to prolong their life. And by all means, enjoy them!! As I said above, they look amazing, but I wanted you to be fully aware of the possible downside to buying them

.