Like many others, I am currently playing around in the Mists of Pandaria Beta and though I would share a few thoughts. This is not my first beta. I participated in the betas for Fallen Earth, SWTOR, Rift and Tera. I have also played a couple of recent demos from Mass Effect 3 and Kingdoms of Amalur: Reckoning.
I have leveled several toons through the Panda starting area and created a pre-made level 85 to test out the level 85+ content. Overall, I have had few issue other than the Burning the Scroll quest, that everyone was stuck at for several days, and a couple of bugged quests, including one that is sometimes bugged on the live servers as well. Of course there are the times that I could not log in and the usual server disconnects that as sort of expected. The spawn rates on many of the quests mobs are jacked up high enough that there is usually not much difficulty in finding enough mobs to kill. In some cases when there are not a lot players logged in, the spawn rate is a bit too high and you have a bit of difficulty in getting away from the mobs. I have noticed that the class balance is off, even in the starting area but haven’t really played around much at the higher levels.
The big thing that I have noticed between this beta and other or even demos is that things are actually buggy and you don’t really have to look hard to see things are off. Other betas I have been in, usually appear much more polished and have fewer bugs. It may bee that I did not get into those betas until later in the testing cycle. I am more inclined to think that those betas were being treated more like demos than betas. Several other people have mentioned this as well. One of the best write ups I have seen can be found here, although leaning more to getting beta access as a perk of pre-puchasing. http://www.manaobscura.com/2012/04/11/pre-purchase-for-beta/
Are developers using beta access and another demo or are they actually seeking help in developing a better game through thorough stress testing in a beta?