If i remember correctly its like the smallest combat boost for the first hit - also getting behind somebody, avoiding mobs, it's tamed horse, gaurds, pavement, any self-interaction, all which causes you to unstealth to then proceed in combat without a horse, it's probably worth giving that small 'suprise' boost considering the trouble you go to to even get there. lol
I actually do stealth a lot, and I wouldn't consider it OP unless there is a well planned long awaited gank on somebody, but even then the chances of being unstealthed outside of them simply seeing you is pretty high unless you know what the hell your doing and plan accordingly your route etc. Nothing really OP about 'stealth' itself, but I can see the worry of the 'back stab bonus' but eh, it's in the code, could be working already and nobody knows, but just wanted confirmation, if its something that is gonna do 20-30% damage against sotg, i'd say no to it.
It's not OP at all, but currently, with BC/Logic checks, you will fail 99% of the time moving whilst stealthed, you will simply be spotted and show up in local, even tho you aren't aware you've been spotted, because you don't unstealth or anything to indicate it.
I think simply removing the mind logic check/stealth check or reducing the effectiveness/range will be enough to bring it into line and 'balance'