elynross has a cool entry on the recent ep here, in which I blather. The thread sort of tries to decide between: "Must All Lesbians Die?" versus "Hey, Lesbians Are Just Evil People Too." I am pitched in the first camp, but we were using Tara's death on BtVS to contrast how "death of a lesbian" is not the same as "lesbian death." In other words, Tara was not a stereotype and neither was her death laden and contextualized with traditional lesbo-spiking imagery.
I mention this because on the bus home I was thinking of another example: "Chasing Amy." I love that movie. Love, love, love it. And if you just summarized the premise--lesbian falls in love with a man--you might wince, thinking they're going to do this whole redemption through heterosexuality story. But you can't watch the movie and reduce it to tripe and stereotypes, because the characters are complex, and because the movie meta-comments on itself and fractures any attempts to read it as that type of story.
To me, any work--TV ep, movie, book, whatever--has to work and earn some credibility when it comes to playing around with old stereotypes. And I don't think Smallville has.