Over the last few weeks, I've been collecting opinions on female comic book costumes and the treatment of women in comics, not only with the poll but also with posts on ThatGuyWithTheGlasses.com and LiveJournal, and discussions with people I know in real life. While everyone has a different opinion on the topic, there were a few points on which everyone could agree.
1. Costumes should be plot- and character-relevant. Zatanna's costume, although it shows off all her assets as much as possible, makes sense for her character, because she is a stage magician, and a performer should always try to draw her audience's attention. She also doesn't make a habit of attempting physical combat with an unprotective costume; her powers can be used as a distance. On the male side of things, Robin's original costume, which would certainly be called sexist if Dick Grayson had been female, makes sense because it is based on his costume from his days as an acrobat. On the other hand, a costume like Donna Troy's, with its inexplicable plunging neckline, or certain incarnations of Supergirl's costumes, do not appear to be at all influenced by character or plot decisions, and serve no purpose other than the titillation of the readers. (While titillation can be a fine motivation, that sort of thing belongs in a very different kind of comic.)
Zatanna, Robin, Donna Troy, Supergirl
2. The anatomy of these women should be drawn correctly and accurately, and not distorted solely to show off their assets. Gotham City Sirens has been a particularly bad offender on this point, with contorted poses that cannot be duplicated by the human body. Many drawings of Power Girl, well-known for her impressive endowments and the "window" in the chest of her costume, do not seem aware of what such a large bosom would actual look like, and also ignore basic laws of gravity.
In this image: Power Girl. This was in fact drawn by a woman, and one who is generally an excellent artist, but something is definitely off with Power Girl's anatomy.
3. When an artist draws a "cheesecake" shot (an image designed to show off a character's sex appeal), this image should make sense in the context of the story, and should not detract from the dramatic tension of the moment. When, at the end of Zatanna #1, there is a panel of Zatanna undressing as she prepares to relax in the bath after a stressful battle, that's completely fine. It's in-character and appropriate for the calm and sensual atmosphere of the scene. When (and I'm deviating into Marvel territory here, because it's a fine example) there is a panel showing nothing but She-Hulk's posterior in the middle of a tense and politically charged argument, that is not only tasteless, but also distracting to anyone who was actually trying to follow the plot. And even the first, tasteful kind of cheesecake shot should be used in moderation. If half of the pages in an issue are devoted to semi-naked women in plot-irrelevant scenes, then that isn't much of a superhero comic, and it is off-putting to readers of both genders.