7/4 actually, when Gilmour solos the song goes into 4/4... This was because Gilmour had a hard time composing a solo for a 7 beat form.
Anyway, prog is rarely in 4/4... And the time sig variety is off the map, Crimson have some of the best time signature variety i have ever heard, all of the songs on Larks Tongue's In Aspic makes extensive use of 10/8, Happy With What You Have To Be Happy With is in 11/8 and Cat Food is in 19/8.
Thela Hun Ginjeet has different merabers playing in different time sigs at the same time (primarly 7/8 and 4/4) to create an off ballance effect and a "fragile" beat.