Big clits are pretty hot -- easy to find and oh so sensitive. The typical "roid voice" is a bit of a buzzkill, but I love deep feminine voices. Tomoko Kanda, who's natty because the JBBF are really strict about gear use, has a deep lady voice that sounds like Kikuko Inoue, and it's toe-curlingly sexy. Amber DeLuca has an attractive voice also -- real husky, sounds like Elizabeth Peña or Kathleen Turner in her prime.
The increased sex drive is also hot. Combine it with a fun, confident personality and it's hard not to be wooed. I should add a caveat to my previous remarks: the right personality can more than make up for a TON of physical deficiencies. I've met fbbs whom no one would call extremely feminine or conventionally pretty, but they were an utter delight to be around.