"And if you drag a folder of images into iPhoto 5, the app uses the name of the folder for the roll name."
The old iPhoto would do this, but only if you dragged the folder to an empty spot in the Roll column, and only if you dragged just one folder.
To me the biggest gain is the ability to import movies. Up to now I've been using my own script to copy photos (it divides them into folders and prompts me for new meta-information everytime there is more than half an hour between two photos) and indexing with Portfolio. Without movie support I'd end up with some camera content in iPhoto, and some stored elsewhere. It made no sense.
But does it support audio clips embedded in stills? (I suppose I'll find out soon enough, my copy is due to show up at the door on Monday.)