I'm not really a big supporter but I see her as being the best and most viable choice compared to the GOP clown car, except for maybe Jeb Bush.
Those of you who want Clinton to win the Democratic presidential nomination in 2016: If you could be guaranteed that she'd end up winning the nomination in the end, would you prefer that she sails through with no serious challengers (thus allowing her to focus on the general election from day 1), or do you think there's actually some benefit to facing some competition in the quest for the nomination (thus, arguably using the primaries to sharpen her skills as a candidate)?
She definitely should not allow herself to become complacent and arrogant, another 2000-style scenario would be a disaster. She would do well to borrow Obama's advisors and get some debate prep (just not with Kerry, heh).
If the primaries are just an extended coronation I see no point in having token opposition, it would just be a waste of resources that would better be used for the general election.