my brother and SIL have my Neice in a porta cot full time as they dont have the money to buy a proper cot and i told them that the mattress is to hard for my neice so they went to clarke rubber and got a foam piece to fit in the cot and that works great.....

When DS was ready for the cot we didnt have one so we put him in the porta cot for a few weeks and it didnt bother him also like raven i used to put extra soft blankets under the sheet to softern it up
but thinking bout goin to clark rubber myself as we go away a fair bit n DS sleeps in the portacot