I've been using these bearings on my bikes for a few years now and love them. Costs just a little more than Grade 25 and the performance is noticeably better.
Helps with mediocre hubs like Shimano 105, but put them in a Campy Record or Dura Ace and the performance is phenomenal. You really notice it when you stop pedaling and coast--you just strooolll on!
Grade 5 might be an improvement but that's cost prohibitive with diminishing returns. This is a nice balance of price and extra performance. A LOT of bang for the buck.