Faebook has a sign up form on the front page itself? has any body done A/B test on something like this vs. another page loaded for the sign up form?
You can't automatically re-use A/B test results from one company for another... Facebook can show a sign-up form without a site tour because everyone knows what Facebook is. A small company just starting out is probably not so lucky.
If you can get results from a company very similar to yours, in a very similar market, then maybe you can reuse their A/B test results. But the best thing would be to run your own A/B tests, and engage with customers over a more rich communication channel (phone, usability tests in person, observing users interact with your site in their homes, etc).
A side note, long term I think the signup form will die. Intuitively what Luke Wroblewski says in that article makes a lot of sense, but getting it done may be hard.