Maybe I'm too naïve.... when you put "free" in quotations in regards to "free" first class travel, what expenses are you considering that make it not free? Booking fees, Credit Card Fees, time consumption? Anything else? Just booked a Business Class trip UA/TK SFO-IAD, IAD-DXB with a return MLE-SFO using Miles accrued mostly through CC signup's. Ultimately my flight is far from free, as we purchased $800 worth of miles (40K) to supplement balance and make it happen, but it's cheaper than any of it would have been for paying even an economy fare, and I had the option of transferring UR points instead, just decided not to.
I know TPG gets a lot of flak for his over-promoting of the CSP, but that card and a combination of others have made this upcoming trip possible for me (at least the comfort of business class portion of the trip)
...of course it did take a lot of CC spend to get there, and I wonder if that's part of where the skepticism about anybody being able to fly first class comes in. and the trip is going to be significantly expensive factoring in food/seaplane transfers and activities, so it's not for everyone.