Well, to some extent we see very, very good value (usually 1:1) exchanges on Coupon Connection. Go there now and I bet you'll see at least three posts on the main page offering 25K or 50K on one program for equivalent mileage on another program. Usually this only works in big chunks because you're essentially ticketing an award for eachother, but its the best value in exchanging around and matches supply and demand with pretty much 100% success from what I see on CC.
I think that instead of building a competing firm to points.com there is a lot of potential and room to improve the exchange mechanism on Coupon Connection. However, FT is always kind of teetering on the edge with CC because the exchanges therein are usually beyond the pale of the T&Cs of the FF programs. I'm not sure Randy would be crazy about formalizing it more...
So yeah - it sucks that I can't exchange my 13K US miles for 5K NW miles somehow, but for larger blocks trading on CC seems to works pretty well.
peace,
~Ben~