In my opinion, The phone was worth every penny. This is still considered a high end device, and to have it on a prepaid, No contract provider for only $35 a month...You can't beat that. I have been with Virgin Mobile for a LONG time..Originally had the Optimus V, Then the Triumph, and previously the Evo V 4G. You can't really compare the phone to anything else VM offers as it's in it's own league in my opinion. Like the previous guy said, It really depends on your signal with 4G LTE. I live in Long Beach, California and consistently get 20MBs on their network. I have ONLY had 1 dropped call with their service since I've had it and it was during the tower upgrades.
At any rate, It's a phenomenal phone with endless features. The camera "In my opinion" is second only to the Iphone. The HD video recording and camera are very sharp, clean and fast. The phone does it all...What I would do is read the thread within this same forum labeled "What feature do you like most about your S3". The things the phone does is unbelievable.
In regards to root, It may be a little bit of time for the rom base to take off as it's relatively new, However there are some out there.. In terms of is root necessary to make the phone work the way it should..No. That was the motorola Triumph and Evo V...Lol.
Good Luck and hopefully we'll see you around!