I don't have beta access, but I have downloaded the client and I can get to the menus. The highest resolution I can choose is 1920x1080 even though I have a nvidia surround setup. So it looks like at least the beta doesn't support nvidia surround.
I can verify, I have a nvidia surround and eyefinity, multi mon does
not work you can not force 5760x1080.
The game is locked at 1920x1080, what a waste I am looking forward to Torchlight II anyways they have broken D3 with so many things :(
Here is a shit load of screens for those that want to take a look as its from my beta session.
http://renewsoft.com/d3/
I am going to try the none full screen mode you guys talked(supposedly 5760x1080) about, I swear I tried that and it does not work, if it does I will make screens and post.
Update: I tried the window mode you can not run D3 @ 5760x1080 in window mode or full. You can only stretch it a bit past 1920 on the width in window mode, really it makes not much of a difference.
Update 2: It does work in 5760x1080*window) there is a bit of weirdness but I go it to work will post a link to the pics in a few minutes. The rendering is not perfect there chunks that are not rendered, dungeons work the best and large towns etc.