Is this extra-firm foam mattress comfortable for side sleepers?

Be upfront: it is not built for side sleeping. Pressure relief scores a basic 4.9/10 because an extra-firm 10/10 slab barely contours, with under 2 inches of sink, so there is no cushioned cradle for the shoulder and hip. Side sleepers, lighter bodies, and anyone with sensitive pressure points will likely want a plusher bed. It is deliberately a firm-support mattress, so choose it by sleep style, not by softness.