well i definately do not blame you for not wanting to get wedged into an iphone!

i would do everything to prevent that from happening as well
as for PB31IMG,when your s-on it does a number of security checks,most of wich will fail with errors,rather than siliently returning to the hboot screen.
is it givin you an error of some sort? is it finding and checking the file?
it could be the main version of the upgrade is older than the main version in your phone. it could be corrupt,and not passing the signiture check. if you happen to have hboot 1.02 or 1.07 it oculd be failing an hboot check.
at any rate,thats one of the beauties of being s-off

you cAn flash whatever firmware you want,whenever you want! :smokingsomb:
i would definately run the phone completely stock for a couple days after running the ruu. if you still have prollems,try a factory reset from hboot. hopefully that will clear some tihngs out and make it a lil happier.
if everything is fine after a few days,then you can easily reroot.
if you want to stay pretty much stock,except for root access,it is possible to boot recovery into phone memory without actually installing it. you can then flash superuser from the booted recovery,keeping the stock recovery on the phone in case OTAs sneek up on you,and/or you need to call vzw customer service. if you want i can go over that with you at some point