Installed the beta this morning, have been loving it ever since. Finally, I can hide my taskbar full time again! Have missed this. Couple of minor bugs I've picked out, though, with the understanding that this is a beta, and so I'm still pretty much happy as a clam over here.
Bugs:
1) Ctrl+Click on the system tray icons (which used to bring up customization options) simply crashes my dock, regardless of the icon in question.
2) Minimizing icons to the dock isn't capturing Explorer windows for some reason, though they show up if I show all running icons on the dock. Minor annoyance for now, I trust it'll be fixed by the final release 
3) For some reason I can't get the tab-dragging feature from the video to work without crashing my dock, either.
Stacks docklet seems to be broken, too, though I doubt that's Stardock's fault. Just a side note.
I'd like to second the request for Categories, too, as from what I can hear it sounds like a good feature that would fit well with the rest. Other than that, it's good so far, bound to be better, and looking forward to the final product - meanwhile, it's become my full time dock.
OS: Windows 7 Home Premium x64