I'm in two minds about this.
I don't like the attention thrust upon them. In a way, we'll never, really know what Cherie Blair was like, she was portrayed in a very negative way. She, like Hilary Clinton, was a feminist and a prominent woman in her own right. And was given a lot of negative coverage because of that.
Eleanor Roosevelt used her position positively. And why not?
There's always a lot of attention, mostly negative, on the women-of-men in power. And the negativity seems to ratchet up a notch if the women are anything other than a subservient doormat. Which speaks volumes about ambivalence about women, if not downright sexism.
Sarah Brown has had to tread very carefully - and she's managed it very well.
I actually hope it will be OK for Samantha Cameron, should she be the next PM-wife (as looks likely). It's a position fraught with difficulty, just because they're female. People/media seem to project so many wants/desires onto these women, it's impossible to fulfill them all.
Doubt very much she'll be pushing herself forward, though I'm not sure she'll be allowed to remain invisible - by either her party's PR machine, or the media.