I have got the standard sport seats, yes i agree they are firm and the cushioning could be improved and the headrest are not very supportive, i also agree i have found other seats more comfortable (M3 and 5 series much better) i would rate them either a 7 or 8 out of 10 but i definitely do not find them uncomfortable and i spend between 2-3 hours a day in my car 5 days a week.
RDT its very disappointing to hear that you find the car so uncomfortable and you are looking to change the car after a very short period of time, however i can relate to this and in 2009 i changed my M3 for a new 120d and i sold that car within 6 weeks because.....i could not get comfortable!
I personally did not opt for the comfort seats, because i preferred the styling of the sport seats