To me (and, yes, I find her sexy), it's about the fact that she doesn't bark her opinion into a camera. Instead, she dissects issues carefully and is open to long discussions of policy matters. It's probably the same reason I think of Glenn Greenwald similarly....
Judy Berman tackles the pressing issue of Maddow's sexiness over at Salon:
It's true that while the butch-femme dichotomy has already broken down among many younger lesbians -- I'm hard-pressed to categorize any of my mid-20s lesbian friends as either -- Maddow is still a butch in my book (and her own). And besides, I think Merkin misses something major about what makes Maddow sexy: the nerdiness! From the "Poindexter glasses" to the Oxford Ph.D. to her perfectly crafted sarcasm, Maddow is as geek-chic as she is lesbian-chic.
I'm not going to make any comments about the rise and fall of the butch/femme in the lesbian community (but have at it in the comments because I'm interested in learning your opinions on the topic), but the geek chic thing sounds about right to me. After the jump is Team Gina's famous tribute to the butch/femme dynamic.