VE's edit surface has a body font size of 0.8em (equals 13px) which mismatches with the new default body font size (0.875em, which translates to 14px on Chrome and Firefox on most systems). The same is true for line-height, which is now 1.6em for body content.
We should make sure the two are consistent. The body font stack and heading settings do get translated to VE edit mode correctly, so we're close. :)