Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Did you ever get it to work? When I did it, it appeared "stuck" and 20% and then 60%. It stayed on each said percent perhaps 2-3 minutes each, but it eventually completed. Have you tried with a different cable? All of my cables can be touchy (the lightening connector doesn't seem as robust as the older 30-pin).

So when you start the jailbreak process, your phone has been updated/restored to ios 8.3 and was "set up as new phone"? Meaning, when you start the phone after the restore (not a restore from backup), it takes you through a whole process up setting up a new phone (language, system setup, icloud setup, etc, etc). If not, then you didn't set it up as a new phone.

Setting up as "new phone" is optional. I didn't do this and my jailbreak worked. I've never set up as "new phone" for jailbreaking.

From an 8.1.2 jailbreak, I restored to 8.3 in iTunes. I then restored from backup. Then before syncing, I uninstalled iTunes and reinstalled v12.0.1. I then jailbroke using TaiG 2.1.3 (run as administrator). First attempt failed. I simply tried again and it worked. It paused briefly at 20% and then buzzed thru. Jailbreak took less than a minute...iPhone reboot took another minute. Then synced my apps and media.

I have nearly every tweak reinstalled (except Springtomize) and not a single crash. It's all good.

Edit: naturally, I had Find-My-iPhone turned off and passcode disabled. I also left WiFi "on".
 
The thing that worked for is that I did a fresh install of iOS 8.3 without restoring apps it worked the first time. Previous to that I was trying and getting stuck on 20%
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.