the fun of Diablo games really comes in the end-game/after-game with item collecting (not really everyone's bag of tea). So far with a level can of 13 we really don't get to see much of the game at all or what items will be implemented. So far it's not exactly fun to beta test because very specific systems are being tested in a very narrow range. While I enjoy what we can access (Comparing a lvl 13 experience in D2 to D3) , there is so much that is shrouded right now that I'm still excited to see if they can pull off the rest of the game.
That said so many of the systems are getting simplified, and that worries me that they may simply over-simplify, and wipe the appeal away. No pet scrolls, less crafting mats, simplified runestones (not runes, but runestones), simplified tooltips, simplified base stats, etc. I hope they don't make it too easy, after all with D2 the devil was in the details.