So yes, I bought a budget mattress (two actually) for my step-daughters bunk bed. They sleep in it every fortnight so I thought they'd be ideal mattresses but I was kind of disappointed.
As soon as you lie on it, or even touch the top of the mattress, you can really feel the very prominent springs. I've since bought quite thick mattress protectors and they've really improved this issue. Other than that, they are comfy, and they were very conveniently packaged which is a great feature for delivery.
Overall, I can't complain considering what we paid for them.
I would recommend to a friend but only if it was for occasional use.