Haven't they been working on this for a while?
There are a number of surveys that have attempted to rank the presidents -- here are a handful:
http://www.americanpresidents.org/survey/historians/ (performance within context of times is probably the most relavent, though some of the others are interesting)
http://www.opinionjournal.com/hail/rankings.html
While Reagan is ranked fairly high, I'm not sure it's high enough to justify putting his face on the ten-dollar bill this soon.
And this is just me, but I don't really like the idea of having recent political figures on currency, regardless of political party. What's wrong with the old guys?