Although I haven't done any logging, I haven't been able to notice a difference with /s 4 (Spiritual Guardian) either, and I've been trying it out a lot in the past 18 levels.
It seems like all it does is drain your stamina :/
There's a Dunmas Recruiter in Everfrost near the Prison that drops a banner, head, weapon... and maybe another item or two, that look to be for a quest, but Wiki entry isn't filled in yet.