Rooting a Nexus device is one of the easiest things you can do. It's nearly impossible to brick one. If something does go wrong, you can easily flash back to stock or flash another custom ROM. So if you decided to give the N4 a try, you shouldn't worry too much about the complexity of rooting.
I've had the S3 since it was released and I don't think I've run TouchWiz for a single day in all those months. I installed Nova Prime (launcher) and you can do pretty much anything you want using it. You do lose a few of the TouchWiz widgets, but I wasn't using any of them anyway (and there are replacements readily available on the Play Store). Maybe give Nova or Apex a try and see how you like it then?
Wow, that's REALLY good battery life for the N4. What ROM/kernel combination are you running?
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And this is absolutely atrocious battery life. I'd try another ROM/kernel combination for sure. Maybe AOKP/AOSP with one of the tons of other kernels?
I do have the nova launcher, and I do love it a lot. I have it pretty much looking like stock Android. My only fear is when key lime pie comes out and it take samsung and att 8 months to release yo the note 2.