No discernable loss in power. Great for all but mud. Run at about 8 lbs. Several friends with razor 1000's and they appear to wear very well! In short I really like them and would buy them again. Make sure you get the aramid version.
6+1 front, 5+2 rear, no spacers. I considered 6+1 all around with inch and half spacers on the rear but wasn't sold on spacers. It would be the better way to go if you don't mind spacers.