Very problematic, but I think it makes it all the more interesting. Especially the last few strips have been interesting to me, with her dragging Marten to the piercing shop and all. It definitely shows that she's more open with herself sexually, but it also shows an extreme amount of confidence that most of the hetero characters (especially Marten, which maybe is why he's there with her?) do no show. Most of the drama in the strip is about characters' self-consiousness about their sexuality, and having a character that doesn't show those same hang-ups is good for the strip, I would argue. It gives something new and fun to pull us out of the doldrums occasionally. And, consider that in most places (in the states, anyway) gay people are still judged much harsher than heteros, and giving Tai this confidence really underscores a strength of hers, as opposed to stereotyping the gay community. Plus, it is a story, and often stereotypes (or, I suppose, archetypes) are necessary, because I would guess most people who read the strip are not homosexual, so this makes the storyline more accessible to them than it would be if she tried to downplay her homosexuality.
In fact, Neil Patrick Harris (how awesome is he?) has been getting a lot of heat from the gay community for playing too many straight characters, and not acting gay enough. If it's really gay rights that you are interested in, it should at least be comforting that Jeph is using gay characters as often as he is, and is definitely portraying them in a mostly positive way.