The beta was just sent out to the testers on Thursday. My friend was accepted, but I didn't find out in time. According to my friend, the improved graphics (640x480 => 800x600) are a definite plus, and the gameplay is different (i don't understand how...) in a good way.
I've been waiting for this game for a while though... I just started playing on Battle.net again because they deleted my old characters (lack of use), so that I'll have strong characters by the time the expansion is released. Oh well, I'm supposed to go over to my friend's sometime soon to check it out, and if the guy doesn't mind too much, I think I'm going to try to extract an ISO from his CD.