I came across a blog last night where someone had been documenting his experiences with the Asus eeeNote. He bought one back at the beginning of January, can you believe it?
Asus really put a lot of work into this thing.
The eeeNote has some impressive annotation abilities including scribbles, typed notes, and bookmarks. You can even do screenshots with and without your scribbled notes, and that sets the eeeNote apart from most every other ereader.
He's shot a bunch of videos and covered the features in extensive detail. (I'm still digging through it, myself.) Here is a video he did on PDF and Epub. It's a little long, though. I think the post is worth reading.