We had those in our library at university (outing myself there!) and they were surprisingly comfortable - you could sit on them quite happily for a whole day of work. But I was 18 then and probably could get comfortable on a rail. Not sure how I'd find them as a 36 year old.
God, I'm now twice as old as I was when I went to university... Thanks for making me realise that, Mum [ wink]