I've got a person (well, a cohort) in my game ready to go into the SF class, so I've been following this discussion with interest, and I was kind of surprised that people thought it was overpowered - on the other hand, the character in question is a cleric (well, Ftr1/Clr4), who is giving up a lot to enter the class, mostly in the area of spellcasting power. (Not only do you lose higher level spells, you also lose the ability to cast spells at range.) For someone who isn't using that spellcasting power, it's a lot more attractive - which suggests to me that the problems might be in the requirements and not the abilities.
J