What do they mean by short play sessions ?
You don't need more than 5 minutes to get 5 NV stacks.
The only reason you may want to play less then 10 minutes at a time would be to chain farm the same area, and it would be very boring.
those screens look awesome, would really like blizzard to change them into something like that, if only it doesn't cause diablo to hog more resources though being able to switch characters quickly in the main menu would just be plain awesome.
I see no problem with TW servers being the first to get this BoA thing tested. If it works well it'll be something we can see happening on EU and US servers too. It's not so much about who get's treatment first, but more about the solution as a whole and a testing ground for it.
Also on a totally unrelated note: real-life ding for me!