|Here's my two-cents worth...
It looks like they will grind for days.
Will they accomodate skateboard wheels?
The wheels on these look more like a rollerblade-type profile and appear soft (for street?)
How well do they turn?
I also wonder how durable they will be in cement bowls, pool coping or just the usual ramp abuse.
They will suck for small feet like mine, unless they come in sizes.
I like the strap-on idea, if it's truly functional.