I don't doubt that the Madone is a great ride: I test rode it for about 15 minutes which was what got me interested in the first place and can confirm what you wrote. And I also don't doubt that chances are my particular BB90, if I were to buy one, would have a better chance at not having an issue, than having one. That said, I would like this aero bike to be the last purchase for a while. I have made a whirlwind of purchases the last few months as I got into cycling, a couple of which I regret and one which I love. So I'd like to make sure the Aero is one I love and want to keep and be problem free for at least 5 years.
You're not the only one to say the Propel is much stiffer (the guys at the Giant LBS also say as much). It sounds like the Factor may be an in-between-the-two bike, not as comfortable as the Madone, but not as stiff as the Propel.
Or I could wait for my temporary desire-to-purchase madness to pass and wait until 2020-21 and hope Trek migrates the Madone line to the T47.
