Transgender is really more of an umbrella term for various identities. Transexual is more likely to be the term that people would forgo in favor of woman, or man (they may also identify as FTM, MTF, etc.). In any case, since this poll is asking about gender, and not sex, I wouldn't worry about it. In my experience, most folks who would think to answer something other than man or woman would know what else would apply to them.

In response to someone else's question regarding the "not sure"s: while people are likely to select that answer for the hell of it, there are folks that do really fall under that category. Among them are nongendered and intersexed people (although intersex really is about sex and not gender).

A few decent links from Wikipedia:
- Sex/gender distinction - Wikipedia, the free encyclopedia
- Transgender - Wikipedia, the free encyclopedia

All in all, I'm glad this poll was posted in the way that it was ^_^. Yay for inclusive thinking!