I've been using a factory unlocked Verizon iPhone 5 on straight talk since day the iPhone 5 came out. Yes the Verizon iPhone 5's SIM card will work with staight talk. For some reason the Verizon version of the iPhone comes fully unlocked, no need to jailbreak,etc.
All you gotta do is either call or go to straight talks website and order the micro SIM card for $10 or $15 bucks. When u get it be carefull and trim all the non copper parts of the Smcard (using sissors). Next takeout the nano SIM card of your iPhone 5 and place it on top of your straight talk SIM card, making sure you have it lined up facing correct direction you will notice your straight talk SIM card is only slightly larger now. Next you must trim off a tiny tiny sliver of the copper chip on all 4 sides ( other only cutting the top or bottom to make it match the nano is card will result in ruining your new SIM card). After you trim all 4 sides , you need only to do 1 last thing in order to get it to work. Looking at the iPhone nano SIM card, you will notice 1 corner has a 45 degree angle, you must make 1 last tiny cut to match this on your new SIM card. After that. Try to place in the SIM card tray. It should fit nice and snug. NOTE ( make sure you trim tiny tiny tiny slivers off at a time, you can always go back and take a little more if it doesn't fit first time) this whole process was easy and painless and took less then 10 minutes.
I have been using this service for 3 1/2 and love it. I cut my verizon bill Down from $220 a month for 2 iPhones to $90.
I can corferm using verizon iPhone, you get 4g speeds up and down, as long u in service area, it even says 4g, and same for 3G. I've used 4gig a month per phone without any problems ,slow downs etc.
I own a semi truck company and travel east coast. T west coast on a bi monthly basis , and service works everywhere on I10/20 I40,I80 from California all way to east coast, on all 3 lanes of travel.
There are a few areas in your 3,000 mile journey where you loose Internet for a short time 4-5 per lane and2-3 no service for a few miles, but the othe 99.99% it's great.
You do loose visual mail, but maybe it's fully supported it may work, I'll have to mess with it.
No hotspot feature, gotta wait for jailbreak, but FaceTime works, and. Mms.
Hope this helps someone.
Here is a link of detailed instructions, NOTE ( you don't need to use sandpaper to reduce the SIM cards thickness, worked fine for my 2 phones without it)
http://www.ehow.com/how_12209600_make-iphone-work-straight-talk-e71-sim-card.html
Rurik