Hi ddt972,
A flexible slat system under a mattress can change the feel and response of the mattress compared to a rigid non flexing support system (which would be a more common choice for a latex/polyfoam hybrid) but this can be either detrimental or beneficial depending on which combination is the best match for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences). A flexible slat foundation is an “active” part of a sleeping system just like any of the other layers in the mattress itself that compress or flex under your weight so it can certainly affect the feel and performance of the mattress. You can see some comments about flexible slat systems vs rigid non flexing foundations in post #2 here and post #2 here and post #13 here.
The only other caution I would have with Ikea beds in general is that the center beam doesn’t have support legs to the floor so I’m not certain how they would hold up over time without bending or sagging but this doesn’t appear to be an issue with this bedframe because based on the instructions here the center beam seems to be supported by the interior framework of the bed…
Phoenix