I don't see anything wrong with giving people hope. If we don't believe we "can," there's not a lot to get out of bed for in the morning. Inspirational messages do have their place--as long as they aren't confused with substantive proposals. Give Obama credit here, he does actually have substantive proposals on his web site. Even if you disagree with his proposals, I think you have to admit that Obama is a reasonably smart person who has put his proposals out into the marketplace of ideas.
I disagree with the idea that he is trying to sneak his agenda into the White House using inspirational speeches. I don't think it is reasonable to expect candidates to use their stump speeches as anything other than a cheerleading session. Substantive proposals belong in writing in a publicly accessible place. Their absence in a speech is probably more an indication of the brain-dead state of the American electorate than an indication of the quality of the mind of the politician.
I don't think that Obama can reasonably be called a demagogue. I think that would only be appropriate if he were either trying to sneak in an agenda under the radar, or if he intended to implement a different agenda than is on his web site. I don't believe that either of these is the case. If he were trying to sneak in an agenda, his web site would be an awfully strange place to expound upon it. And I think he believes that his proposals would work.
(All of this is written by someone who doesn't actually plan on voting for him on Tuesday, and who may very well be voting for a 3rd-party candidate in November.)
His lack of experience in military and foreign policy issues is a totally different (and legitimate) issue to explore.