It's a good move and worthy of support. But it does beg certain questions (like: If Obama thinks it's right for Oregon to set its own laws regarding pot, why doesn't he think it's right for Mississippi to set its own laws regarding abortion?)
It's when the states want to shut down individual and civil liberties that the federal government should intercede.
That said, the feds should get out of the way and let the states vote on their own drug policy to it's logical ends.... decriminalization at least.
They'll HAVE to, anyway. The U.S. prison population has doubled since the 1980s. My state of Massachusetts alone* pays out 1.25 billion a year to incarcerate people, at least half of which are in jail on petty drug 'crimes'. Under our last governor Mitt Romney, 'corrections' expenditures topped higher education's share of the budget.
*and Mass. isn't the worst. That odious honor goes to Georgia, which has one out of every 13 of it's people either in jail or on probation. The war on drugs crowd is also the 'smaller government' crowd.... but they haven't figured out yet that those goals are at odds with each other.