Just made this discovery last night: It's not that you go faster (I didn't) - but that they corner SO much better! I switched from a wheelset with straight 14g spokes to one with DT Rev's (rims and hubs were the same), dropping about 200 grams in the process. It's just so easy to lean the bike in the corners. I felt much more confident coming down switchbacks. Well worth the change in my opinion.