This is what I believe to be accurate at this point, if anyone knows differently and can point to a reliable authority for better information please share. You often have to listen very carefully when promoters of the plan talk about it. There is a lot of "happy talk" about the ACA, but not a lot of clarity.
Many transgender people have been blocked from getting coverage for pre and post transition related care, including blood tests, gender therapy, HRT, etc. These things should all be covered without any issues under ACA, since to fail to cover them would be discriminatory. Meaning if a modality of treatment is covered for any insured, then that same modality of treatment cannot be denied to a person just because they are transgender. For example, if an insurer covers psycho-therapy for other conditions, they will not be able to refuse to cover gender therapy, and if an insurer covers HRT for a menopausal CIS-Gendered woman, it will have to cover HRT for a TRANS woman.
Many large corporations with the better insurance plans have in recent years been increasingly signing up for the HRC CEI (Human Rights Campaign's Corporate Equality Index) standard which requires at least a $75k lifetime benefit for transition expenses, which can be used for SRS, FFS, and other transition expenses. In 2012 the HRC reported that 189 large employers were fully supporting these costs, and in 2013 that number grew to 254. The problem is that these tend to be the so-called "cadillac" health insurance plans, many of which are going to be dropped as a result of the increased expense under the ACA, forcing their employees into the ACA exchanges, and at this point the ACA has not committed to the HRC CEI coverage standards or anything close to it. My employer has already announced that we will be losing our current very generous health insurance in 2015 when the deferred employer mandates kick in. If you were to hire on to a company who currently does support the HRC CEI, hoping to get FFS and SRS coverage, you could be disappointed to discover that coverage being dropped.
So while more transgender people may get some some health insurance coverage, many may lose the ability to get transition related surgery coverage which they already had. ACA tends to look good for the un-insured or poorly insured, or those with other insurance challenges, and not so good for many folks who already have good insurance. At best there is a great deal of uncertainty about what is going to be covered, what the coverage will cost..