I am very happy that Thomas decided to go public with his "pregnant man" thing. Personally, I believe that our culture is very messed up about gender. I think that we should think of biological sex as completely different from gender. I don't think that we should require people to adhere to binary gender (either "act like a man" or "act like a women") nor require them to adhere to the gender expectations associated with their apparent biological sex. I know that many people here think that Thomas is doing things both to mess up his children and mess up societal expectations of gender, but I think he's doing things that will both benefit his children (give them an opportunity to be true to themselves instead of true to societal gender expectations) and benefit society as a whole. If he wasn't public about it, then he'd still be able to benefit himself, his wife, and his children, but he wouldn't be able to improve society. So I'm very grateful for his willingness to put his choices out into the public sphere.
I lived in an apartment-style dorm with a male-to-female (MtF) transgendered person (and, additionally, a person who became a female-to-male (FtM) transgendered person after college). The MtF was quite shy about her gender-identity past. She came back and made a presentation after she left the school, and it was hard because she was also coming out as an MtF to several acquaintances and one of her very close friends. (This close friend was very oblivious - the MtF both showed a transgendered movie to this person and had gender reassignment surgery while this friend knew her, but the "subtle" hints simply didn't work. Actually, the presentation with a bunch of "me" and "I"s didn't work either: it took 'till the Q&A session afterward for the oblivious friend to really believe it.) My MtF friend is legally married to her female partner (they both identify as lesbians) because she wasn't able to legally change her sex, and (of course) because marriage between men and women is legal where she lives.
Deciding to be transgendered is extremely difficult. Deciding to be publicly transgendered is even harder. I imagine that publicly being a gendered female who is a biological mother is even tougher. I congratulate, applaud, and thank Thomas for everything he has done to improve the way our culture views gender. His contribution will help countless children and adults be able to be true to themselves instead of slaves to gender expectations. Gender and sex are not the same thing, and individuals in our culture will be much happier when this reality becomes widely accepted.
Edited to add:
After reading the link to the story about Patrick Califa-Rice's boyfriend's pregnancy, I agree that Thomas is not the first male to give birth. I can see his "legal male" distinction, and it's interesting, but I think he needs to be admitting and bringing up that he isn't the first pregnant FtM. No matter, I still think that his hard work to put his pregnancy out into the public sphere is doing a social good.