Power Holes are a stringer's favorite racquet advance! Yea, right. Actually, it's a slot cut into the internal section of the hoop. It allows the string bed to move a little more than a normal grommeted racquet.
Prince has the Sweetspot Suspension, Volkl has Big Grommets and Head has Comfort Zone, all of which allow the stringbed to float a bit.
The new Power Holes as seen on some of the new N Code racquets from Wilson aren't quite as miserable for the stringer. The slots are there but the grommet is visible without bending over and searching for it when stringing.
When the Wilson rep came in with the new racquets and mentioned power holes, I told him that he was p*****g off the stringer. He showed me that the grommets were visible, so I released him from a figure 4 leg lock.
Rollers are several small "wheels" shaped similar to a rim of a car that are placed north and south of the 3 and 9 o'clock position. The littel buggers actually rotate on a small shaft that is integrated into the frame. The theory is that the string will move easily on the roller allowing the string bed to be more resilient.
Truth be known, Wilson did it just to aggravate stringers.
David's right about the Power Holes. They're a stringers nightmare. When Silent Partner sponsors that speed stringing contest, they should have to use Power Holes. This would be a good way to hear new 4-letter words invented.