Although the question was addressed to Leigh, I can say one thing that changed for me over time, even before I was consciously aware of wanting to transition, is that a lot of the older feminist materials have a real gender binary. It's very much woman good, man bad. It also has a hierarchy of rights. Under older feminist theory, gender is the primary divide. Race, ability, orientation, social class, gender identity are secondary.
The newer feminism takes a more deconstructionist approach to gender and doesn't require buying into the binary to accept. It also allows a more holistic concept of equality, like in Alchemy of Race and Rights, where there isn't a hierarchy of rights, like gender, then race, then ability, then sexual orientation. Some of the older feminist theory doesn't fit well with women of colour or lesbians, because it basically ignores the "other" difference or relegates it to a different theoretical perspective, so that if you have more than one difference, you have to try and choose between theories or force them to fit.
An example of hierarchical approach to rights was a legal case in Canada, where a wealthy female lawyer challenged the law that made child support taxable. Most recipients of child support are women. Statistically speaking, most women are worse off economically than men. The tax regime where the payor deducts the child support (thereby not paying tax on a higher income) and the recipient pays tax on the child support (at a lower rate) is a net tax savings to the family. It only doesn't work when you have a rich recipient. Nonetheless, this wealthy woman challenged the law and succeeded. Now lots of poorer women get less child support because it's not a tax deduction to the payor so the payor can't pay as much. The Women's Legal Education and Action Fund supported the wealthy woman because most recipients are women. They completely removed economic status from the equation and it didn't even occur to them until years later that although it might have looked like they were acting for a woman, the result of their intervention was that poor women in relation to rich women suffered.
I got in a huge war with the chair of Women's Legal Studies in grad school because I wrote a paper critiquing some feminist legal theory and the necessity of buying into the gender binary in order to make it work. The result was gross injustice to transsexuals and, to some extent to gays and lesbians as well. She trashed my paper and I had to actually appeal the grade to change it. First and last time I did that. I left grad school shortly afterwards. Re-read the paper later and came to the conclusion that the prof simply didn't understand it because she couldn't get her head out of the binary system.
That sounds perhaps a little odd from someone who has transitioned medically and socially, but just because I'm on one end of the gender continuum personally doesn't mean that I buy into the gender binary and think it's universally applicable.
Dennis