I've never really heard of installing SRFIs (could be my ignorance); do you mean importing them? Or is installing SRFI implementations as their own packages really common? (Haven't really tried R7.)

The anti-R6/R7 folks (or what I've heard) won't see a problem so long as you can use CL to build fancy serious software, which lets Scheme stay small and simple for education. (Of course ideally you'd be able to do any SICP exercise on a Scheme implementation out of the box, though.)