They're fine if you only need it for a year. I found their $200 Morgedal mattress very comfortable and I slept very well on it, but about two years after buying it started to get super saggy and worn.

Cheap foam is why (what can you expect for $200?!). My parents got a 100% foam queen-size mattress more than 30 years ago, and it's still in very good shape with full-time use. They flip and rotate it every month or so, which probably helps a lot (most mattresses today aren't supposed to be flipped). I think it cost about $1000 in 1989 (about $1800 today).

IKEA has cheap mattresses and expensive mattresses, their expensive mattresses are quite good, but, you know, expensive.

In general, I find IKEA stuff to either cheap or expensive, and you generally get what you pay for. I have a loveseat, armchair, and coffee table from them -- the loveseat has lasted for about a decade and (aside from a few cat claw marks) is as good as new) despite costing in the realm of $1000USD, the armchair was cheap and the bolts on it need frequent tightening, and the coffee table is $30USD of paper yet inexplicably has also lasted almost a decade.

A lot of furniture from IKEA is just way too damn stiff/upright to possibly be comfortable unless you are a contortionist. I don't buy anything there without sitting on it first.