I did put this on the sofa bed that I ordered it for and it fit fine, however it has not been slept on yet.  I did put it over a rather thick mattress topper, which I have ultimately returned and decided to use air mattresses over the bed frame instead.  I haven't yet tried it on the air mattresses, but the fitted portion of this cover has very deep sides and I believe it will still be okay.  Only reason didn't give 5 stars is because it isn't sewn perfectly straight.  When I laid it out flat on a KS bed for folding, it was impossible to match up the two sides and two ends with each other.  In other words, it wasn't really rectangular, but more trapezoid-y, which makes it very difficult to fold evenly.  Oddly, this didn't seem to affect the coverage of the mattress - must be that all sides were longer than the mattress'.  Hopefully that will still be the case when putting it over the air mattresses.

Pros: Seems to be a good value
Cons: Not perfectly straight