I've actually been doing things really similarly, Dana.
I've always been a bit girlish for a boy, but that doesn't mean I'm anywhere close to passing as female. I decided that slowly pushing the gender line would make it easier for others to get used to the changes, give me time to figure out my style and true personality, and give me time to tell everyone bit by bit. So far I still wear jeans and t-shirts outside the house most of the time, but I do my hair in cuter ways, put on a little eyeliner and blush, etc.
I still think that this is the best way for me to figure things out, but there are definitely some down-sides to it as well. Some people have an easier time with androgyny, but it seems like some people would rather I fit a stereotype so they can just switch the checkbox they have for me in their head from "M" to "F". I've also noticed that if I imply that I'm female, even friends who've previously said that they understand will sometimes argue with me, and say things like "Well, technically no," and I end up having to explain that I'm talking about my identity and not my genitals. Then there are the things like voice and pronouns that are harder to switch gradually.
I think it's just tough for people to realize that just because I identify as female doesn't mean I want to go around in high heels and dresses. Sometimes it can be maddening, and I just wish I could get over that hump, where enough cues are in the female range that people just roll with it.
I guess a lot of these problems are pretty universal to transitioners though, and not necessarily just those who do it gradually. =/