So I originally kept getting the Error 132, where your MoP client throws this error as soon as you try to launch it. The download went fine (if normally slow, because, hey, shared apartment connection), but it was the client throwing the error at me.
The fix that worked for me was that my config.wtf file was missing. How to fix:
Go to your live/current WoW folder –> WTF folder –> Copy the Config.wtf file.
Go to your MoP beta WoW folder –> WTF folder –> Paste the Config.wtf file.
Open the config file in the MoP folder with Notepad.
Around the first SET gx line you see, make a new line, and put in SET gxApi “D3D9″ with the quotes. Save this file.
Now try to launch your game client.
Also to get into the beta, the WoW account I selected on the login screen was WoW2, even though the beta client on Battle.net says WoW3.
Poneria is on Lost Isles-US, if anyone wants to know. 
Nice to know. After the last patch my copy just quit loading “file missing from MOP. Goodbye”. I ended up uninstalling the entire build and starting the 25gb download over (before heading off to work).