This was a retelling of Cap's origin story, done just about perfectly in every way. The changes made are those which are needed to make the story WORK onscreen, and to allow for what obviously is an intended set of connections to the future Marvelverse he will be entering (HAS entered, by the end of the film); there are as far as I can tell no gratuitous changes.
The actor for Cap does the role perfectly. This is the Ideal American given a chance to truly be all he can be, who carries off even the most embarrassing assignments (and he does indeed get embarrassing assignments) with as much dignity as can be allowed, who does not want to "kill Nazis", but just teach bullies a lesson, who -- despite upbringing -- is willing and able to see the best in those around him, even when they don't fit his peers' ideas of normal or correct.
As Captain America, he is a warrior par excellence, and they do perfect justice to him in every combat scene.
Hugo Weaving brings majesty and dignity to the Red Skull, a perfect foil of evil for the nobility of his opponent.
This one's going on my DVD to-buy list, and the trailer for The Avengers looks awesome.