Contrary to a number of opinions in this forum:
1. The Carbon Fiber frame on the 7.9 has the same warranty as does the aluminium framed bikes. Break it and we'll replace it. Not for five years, forever.
2. My new 7.9 weighs three pounds less than my wife's 7.5.
I was looking for a 7.9 or a 7.7. The shop where I bought the bike here in Washington charged me only about $300 more for the 7.9 which they happened to have in the shop.
It rides just like my wife's bike except it accelerates faster and handles a little better because of the slightly lower center of gravity.
I discussed the possibility of "hybridizing" a Madone 4.5 but two of the techs in the shop said that's definitely not the thing to do and gave me a number of reasons why, all of which made sense.