Everything, EVERYTHING is % and em. No pixels, no points, NEVER, NO WAY.
A designer sits there with 20-something-year-old eyes, on a 27-inch monitor megacentipixel screen--and not thinking about the surfer, viewing the same content with original-issue-eyes on an iPad.
That content better flow, vertically, with as few as 30-40 characters per line. And the user can, if necessary, work out how to view it.