Back in the day, I was a huge Clinton supporter (by the way, back in the day was like last year), today that has changed. Clearly, Obama has demonstrated that he can do well in the general election. If you examine the coalition of folks that he has brought together, i.e., blacks, whites, young, not so young, Independents, and Republicans (Operation Chaos not withstanding), there is no way that you can reasonably conclude that he is less, not more likely to do well as a candidate in November.
Also, contrary to political spin, the base is uber-important. Given Hillary's early support of the Iraq war, this is an achilles heel for her. White rural Republicans will not vote for a D in November. Period. We will need overwhelming support from our base. Obama has proven that he can not only rally the base, but he can reach beyond it, which is not too shabby for a general.
If you visit my website: http://www.drchuckspeaks.com/ you will see that I have been a huge supporter of Bill and Hillary, ergo, this is not some knee jerk reaction from a person swept up in Obamerica. I carefully considered the facts.
Moreover, Hillary will be able to mobilize the GOP base like never before. The disdain they have for the Clintons is legendary and, more importantly, politically damaging for Democrats. Also, when one considers the number of folks who are voting for the first time, in greater numbers than we've seen in recent memory, that is largely attributable to Obama. We all know this. Let me be clear -- It's not that Hillary is a bad person or a bad candidate. It's that she's not the right presidential candidate for the Democratic party at this time. She must concede. The outstanding superdelegates who have not committed can end this. They should end this. This intraparty bickering cannot continue. We are now hurting the likely candidate and the party for November.
So, any superdelegate who hangs on beyond May, knowing this reality, is a coward!

Hil will stay in at least thru West Virginia, Kentucky, and Puerto Rico. At this point, she is all but assured "free" victories there. This actually helps Obama: it prevents the press from covering him losing to a candidate who has already dropped out of the race. Also, it allows her time for an "in case" strategy: "in case" Obama really effs up.

I think a loss in WV or KY would be about the only thing that would potentially hasten her demise.