Whilst I don't think that transsexualism is a MENTAL illness, I still believe it has to be some kind of issue. Be it a brain malformation, a neurological problem, the aftereffect of an uterine hormone disbalance or something else, I don't believe it to be anything good to have or normal.
I wouldn't really relate it to the situation of homosexuals in regards to treatment from psychiatrists and such, since we, contrarily to them, absolutely require, in part of the cases, at least, medical attention such as hormones and/or surgery to survive with an acceptable mental health.
I don't know about other people of the transgender spectrum, but it's not like transsexuals, at least not I, would suddenly feel better if society were okay with our changing social roles. If that sufficed, we simply wouldn't be transsexuals, by definition. My body is just as harmful to me as how people view me, if not more.
That being said, in my book, anyone who requires medical intervention to function normally has some sort of health issue. Homosexuals, however do not need any medical treatment, except maybe psychotherapy to treat damage caused by segregation, but apart from that, just like any other normal human being, they just need acceptance to be happy.
I'm not saying that I agree with how everything works right now, but I still don't think that transsexualism is a good thing. If one day, they were to discover a way to diagnose a transsexual before birth and prevent them from being a transsexual with hormone injections or something, assuming I would somehow be pregnant, I would be the first to ask for it.
I don't think we should be ashamed of what we are, just like someone with a missing leg shouldn't be ashamed having had a prothesis put on it. But I definitely don't think we should be proud either. Being proud of something means you think you are lucky you got it, that it somehow makes you feel better than others.
Of course, I dream of a world where saying "I'm a transsexual" wouldn't have any more effect than saying "I had a missing leg compensated for". But I definitely don't think that a place where transsexuals willingly place themselves in a different envelope than the rest of society is much of an improvement.
Again, I'm not including any non-transsexual transgendered individual who require an envelope different than male and female or an enlargement of the definition of either in this line of thought, since contrarily to transsexuals, their goal is not exactly to "become as (fe)male as possible", but to become something in-between or something else.