The early Floyd were definitely avant garde - a saucer full of secrets and piper at the gates of dawn show them at their experimental best. There is no way anyone could listen to them, compare them with their peer groups at the time, and not see that they were on the fringes of rock experimentation. Truly revolutionary - questionable in the I want to put it on again and again and listen to it a few times category. In terms of great music, I think Meddle is their best work period, followed by Wish you were here, Dark side, and the vastly underrated Animals. Umma Gumma, Atom heart mother, More, Obsured by clouds, all have some intersting tunes, but in general are relatively weak in terms of songwriting and performance - they seem to have lots of fluff. I condider the Wall and the Final cut to be the band's weakest albums, almost water's solo albums with the band as backup (with a few exceptions on the Wall where gilmour gets to rock). Water's is way overrated as a lyricist and his "social commentary" is transparent and pedestrian at best. With the exception of Gimour's contributions, the songs lack melody and interest. Waters is not a great singer either -mainly talking through many of the songs as opposed to actually attempting to sing. If you want to go beyond Floyd, check out Gilmour's two solo albums - they are consistently good. In general I don't think that Floyd ever sold out - just because you are commercially successful does not mean you are a sellout - listen to have a cigar - talk about biting the hand that feeds!
Cheers - Scott
Cheers - Scott