I sold my iPad mini retina for the Nvidia shield tablet and my opinions are mostly positive. This is my first Android tablet (I've had nearly every version of the iPad) though I've been using Android phones since the original Droid. I actually bought my tablet at Gamestop and I picked up a controller at Best Buy. The controller is very well made and much needed IMO. I will say that I wasn't a heavy gamer on my iPad but I did have a LOT of games and generally I feel iOS has better games in general. I will be getting an iPhone 6 to replace my Moto X though. I like having both platforms.
The game streaming is very quirky. Initially, Limelight worked better than Nvidia's own software. That was until yesterday when Valve pushed a patch for Steam and "broke" it. Normally, I'd launch Steam from the tablet and it more or less remotes into my desktop using big picture mode. Well, after the patch, big picture mode is borked on the tabled due to a resolution mismatch or something. No one has been able to fix it yet though. I can still add games directly using Nvidia Gamestream (on desktop client) but it's a minor gripe.
Battery life has been pretty good for me overall. Nothing scientific at all but it lasts similar to my iPad mini in terms of how I used it. The wider aspect ratio has been the most challenging for me to get used to and the screen isn't as good as as my iPad was but it's tolerable.
WiFi was very off when I first got it but the patch definitely helped. I'm baffled they didn't include wireless AC though. Very odd choice. I'm not having the problem with cracked edges either and I've mishandled the tablet a couple of times as well. D:
I could go on and on but again, so far so good for now.