Spent a day with it so far. Everything about it is lovely, though there's some instability (it really doesn't like folders in the dock!) and there are a few bugs that do annoy (the dictionary definitions pop-up being impossible to dismiss is annoying, but the complete inability to type Japanese text on there might be a deal-breaker for the time being)
I've noticed the dock thing too! I mean, you can put folders in the dock and expand and contract them fine, but when you try and removed items from a folder while it's still in the dock you get a soft restart (black screen with grey Apple logo for a moment). Taking the folder OUT of the dock and then removing what you want works without a problem.
As far as DD, yes. I am running it as my DD on my Sprint iPhone 5. I love it. I'll deal with the little annoyances. I've noticed these nuances in the following apps/features/functions:
FaceBook: When you swipe to the right to get to the shortcuts pane/panel where you would click/tap to go to your wall spazes out until you scroll up and down a little and/or swipe back out to full screen and then back again. That was horribly explained, but that's the best I can do lol.
Skype: You can sign in and do everything except load up a group msg you might be a part of. Dunno about calls. I'll test that and get back to you.
Signal strength: I live in an up and coming Sprint 4G LTE area, and on iOS 6.1.4 I would get pretty decent LTE in my house, and in the front of where I work. I can also get 3g EvDO in the back of work. With Beta 1, unless it's Sprint upgrading stuff and taking forever doing it, I get anywhere from 1x to LTE randomly. The only way to restore a stable-esque network connection is to toggle Airplane Mode. Then it works for a bit, but inevitably and eventually goes back to its antics. <_<
As far as battery life in concerned I'm sort of cheating... lol I have a Mophie Juice Pack Air 1700 mAh model. I can walk around work with online radio I like playing and only about half way through my 8h shift does it revert to the internal battery. I cant' say how my battery life was before I got it/when I was on iOS 6.1.4, but it's not bad at all on the Beta.
There are other small things that plague the Beta, but all in all it works great. I love the new UI as many of us here do, and I can't wait for Beta 2 to release. I'll be the first in line to install it. xD