The screenplay was written by two heterosexual friends, Jennifer Westfeldt and Heather Jurgenson, who both star in the film as Jessica and Helen, respectively. The birth of the premise seems clear -- "What if we were to write a play where a couple like us were in a relationship?" The answer, of course, was "Oh, it would never work, because we're not gay..."
The main characters are Helen, an outgoing, street smart bisexual free spirit, and Jessica, who can only be described as neurotic, afraid of sex, repressed, guilt-ridden, and Jewish. Why must every Jewish character be depicted this way? Can you watch this whole movie without wanting to bitchslap her? No, I don't think so. The character focus is on Jessica, however... why? The inference is that although Helen is who women would like to be, Jessica is who they are. (Note to women: sure must suck to be you.)
Jessica works with her old college flame, whose only redeeming qualities seems to be that he's attractive and smart -- he's also brooding, nosy, invasive. controlling, obsessive... as a friend, he leaves a lot to be desired. They presumably only work together because both of them seem addicted to sniping at each other. He spends the first half of the movie playing the part of that creepy guy in your office who works down the hall...
So, Jessica, a "fine catch" in her own right, comes to the rather stereotypical, sexist, yet popular presumption that all the good men are either married or gay, and decides to answer an ad based not on gender, but on the presumed intellectual depth of the ad writer; depth that was never there to begin with. At least Helen is street smart and shows some signs of self-knowledge; Jessica comes off as shallow and frivolous; so out of touch with herself that she can't even decide what turns her on.
So, Jessica shows up to answer Helen's ad, then proceeds to state that it was all a big mistake, and puts up a nearly impenetrable shell. For some reason, Helen decides to try to crack it, putting up with an almost insulting level of rejection for no obvious reason. One can only surmise that either nobody else responded to Helen's pretentious ad, or that Helen has a thing for straight women... does this mean that she secretly hates that aspect of herself that isn't straight?!
So, the two finally get together, but Jessica, although loving Helen deeply, is not sexually interested in or particularly responsive to Helen's lovemaking. Cold fish. At the same time, Helen has changed Jessica's life - Jessica is happier, more relaxed, and more expressive than she's been in years. Okaaaay.
Eventually things progress to the conclusion that you can't put a square peg in a round hole. Jessica's not gay. Never was... whereas Helen obviously is gay and soon finds a nice lesbian girlfriend. Forget about bisexuality or sexual fluidity for these characters, because once they gain "self-knowledge", there is no middle ground.
And, look! The love of Jessica's life was there the whole time... the old flame / creepy guy! Oh, please.
So, if you are looking for a light, breezy, Sex and the Cityesque, heterosexual-oriented taste of what it's like on the other side of the fence, congratulations... there's yet another film for you to see. Just don't mistake it for the real thing. This goes double for those who should know better...