Six of one, half a dozen of the other. There's some "she's not really a whore; she's more like a Japanese geisha," some "omg, she's so obviously a teenage boy's pervy fantasy, Joss-you-jerk!" and some "clearly this is proof that Firefly has no strong female characters and Joss Whedon is secretly misogynistic."

My personal take on it is that she's Firefly's version of Miss Kitty (you know, to Mal's Sheriff Mat Dillon). Or Josephine to Mal's Wyatt. The whole "soiled dove" archetype is as much a part of Westerns as the "strong and silent hero" and the "shoot-out at high noon."