I'll start this by saying I own the Hero 3, and have always wondered, how much better can the 3+ really be?
I got a chance to test it out this weekend up at Snowbird and it lived up to the hype. I don't know how they do it, but GoPro just keeps making these things better.
Stand out new features:
1) Super View mode: Wider view and it doesn't look boxy or distorted. You can mount it on your helmet and still see your skis without angling it down too much.
2) Low Light mode: This is awesome. Noticeably better picture in off or changing light conditions when compared to the Hero 3.
3) Battery Life: I lent my friend Ryan my Hero 3 while I used the 3+. After our shred, he had one bar of battery left and I had two. I'll chalk that up to a 25% increase like they say.
In the video:
HERO 3 --> Ryan DeVine: Red pants and Rossi skis
HERO 3+ --> Me: Black pants and Armada skis
Both in 1080p 30fps modes
You should be able to see some differences in the two cameras.