Jeff Kaplan, the lead game designer, posted in the forums under his username Tigole that Blizzard will be speeding up leveling in the 60 to 70 bracket just as they sped up the 20 to 60 bracket. This has long been rumored and it's great to see this get implemented.
Initial reports tell us the amount of experience points necessary to progress to each level has been decreased by 30% (for the 60 to 70 range only). Additional posters are reporting that mobs which give 500xp on the live server are now giving 600xp on the beta server. There doesn't seem to be any increase in the XP rewarded by quests yet, but this might be a future change.
Kaplan asks everyone to provide feedback on the change (if you're in the beta), and it looks like they've got his ear for the time being. So if you're in the beta and want to weigh in on the subject, now's the time.
Many thanks to the various users who submitted this news tip.