Downloaded it last night, everything seemed to be going fine right up I had finished the final installation and then the phone just refused to boot up :/ It was just showing the Nokia logo for like 30 seconds, then went black for a while and repeated the process over and over again. Tried soft resetting, battery pulling, removing SIM card and storage card, but nothing worked. After about an hour I'd had enough and just committed to the hard reset. The installation was still successful though, so I have GDR3 on my phone, but had to reinstall all my apps, play around with my settings and lost all my data in games. Moreover, I'm not able to download 'Settings' updates like storage check, display + touch and the like as I get an error code every time I try to download them. So I'm stuck with the original versons of those things. Definitely regret updating it, the new features aren't worth losing all of that stuff at all.
EDIT: Yay, those things have now decided to download for some reason! Only bad thing now is the lost data in games but it's not a huge deal for me.