I have been upgraded to business class 3 times now, purely on the basis that I'm a silver member with Emirates, I didn't wangle points which was a bugger! It's worth it, I'm 6ft2 with broad shoulders and found sleeping a little annoying when sat in cattle class. Although, saying that on these new big A380s and even the Boeing 777s there is enough leg room.
Never flown first class but would love to have a look inside for sure!