I just rooted a friends S4 and was going to install the Google Edition ROM, but it was ME7, so there isn't a boot loader that works.
I gotta say, I really dislike Samsung. They have no clue how to write software. So much lag/animation stutter. It's so jarring and unpolished. The color scheme of Touch Wiz is horrendous. The large screen is very poorly utilized. I can barely see any more of a mobile site on a 5" S4 vs a 4" iP5.
Don't even get me started on PenTile, signal strength or a speaker they can be silenced by a couch...ugh.
I like Android, but Samsung sucks, big time. I can't wait for the HTC One to hit Verizon....or Motorola to magically discover an AMOLED shortage and announce 1080 LCD screens in the DROID MAXX.
I'd honestly keep the iPhone, but no data on voice calls is really frustrating...so is apps not updating unless they're open.