Doha airport has to be a contender for the filthiest place on earth competition. Too many people for such a small airport. There are little or no facilities, and no staff to help. Because of the lack of toilet facilities (there were huge queues,) people had urinated and vomited in corners on the floor, and this had not been cleaned. Hundreds of people were sleeping on floors due to a lack of seating.
http://www.reviewcentre.com/review168737.html
I am only ever going to Doha once - and I've already been. Its not worth the 100quid or so saving. That said the planes themselves are fine.