Well I just rolled back an old Alpha that was incomplete and have installed the beta.. So far so good.. Easy install, activation etc.. Pretty happy so far.
Firstly, everything Nintex all in the 1 spot... awesome..
New Help feature, to help documentation up to date
If you get lost here (as I did), you'll find safe looping under 'Security'
I imported over a form directly from 2013.. Perfect, and look no Nintex Live Forms.. Just External Forms.. 
Overall the forms designer is pretty much the same, but I want to say some of the icons look a little refreshed, and the UI has been super responsive.. (Using Chrome)
As most who can probably read this, you will probably have a good handle on where actions are, and probably use the insert action option more than the drag and drop menu.. I know I do, this has improved, and it is now even easier to find the stuff you want.
This is part is because the Nintex Live Catalog in now non-existent.
and the actions that you used to have to go to the catalog for, are now built in.
You may ask the question "We have these new cool smaller actions, but the canvas still shows large icons"
Well just to let you know that this will be updated before RTM A few icons still need to be updated to the new format and sizing.
