I always thought the very end of Same Time Same Place was foreshadowing Buffy sharing power at the end of the series. Why? Because it wasn't organic to the episode. It seemed like it was deliberately included for a reason.
I had a theory all season that the problem of the Slayer was like "Marie Curie syndrome"--the idea that women can succeed and be powerful/intelligent, but they are special, exceptional, unusual. And when they are presented as such, it's not really empowering to the women and girls out there who might some day pursue similar interests, and it's also damaging to the "Marie Curies" who are told they are special and thus isolated.
Damn, I can't find the original, but I wrote this in December on a Spike list in response to the idea that Buffy might end the series without superpowers:
"I wrote a post a few weeks ago about female exceptionalism. It's all well and good for Buffy to be the Slayer, a strong woman etc., and example of female power, but hell, she's the only one. Or one of 2 slayers. :) Female exceptionalism--the idea that only the extraordinary women can have that kind of power.
Well, with the advent of the SiTs, and Buffy training Dawn, maybe we're seeing that the "potential" to be extraordinary is in everyone, even those without superpowers/superstrength. And I think for Buffy to be the only girl in all the world to fight vampires is, in fact, limiting--for Buffy and for all women in the world. How is that feminist? What Joss may be going for is to recognize that you don't have to have superpowers to be extraordinary, to be able to fight the demons in your life. How is it feminist for Buffy to have to save all the women in Sunnydale? What's feminist is for them to realize they have the power to fight back for themselves, even if they are not Slayers.
Anyway, if that's the case, then Buffy ending the series as a superpowerless human--alongside a shanshu-ed/human Spike--is not a negative thing. She might see that she can share her power with all women. Slayer power is girl power. Or grrl power.
Is it about power? Or is it about empowerment?"
Just realizing, too, that this fits in with the idea of Get It Done, an episode I hated when I first read the script, but worked myself up into a state of respecting it before it aired. That episode was about Buffy being tired of having to do all the saving. Why couldn't the others take care of themselves? They had skills, reserves, powers. And when she went off to the Shadow Men, sure enough, they found that even without Buffy they were able to figure out how to deal.
And that's why I don't mind Spike keeping the coat. It symbolizes a dark side that he draws power from. It's the same thing as Willow doing her magic, even though her previous use of powerful magic led to flayed Warren.