Is the Sealy Spring Medium good for side sleepers?

It can be, but side sleepers often want more cushioning at the shoulder and hip. The medium spring feel is firmer than many foam mediums, so lighter side sleepers may find it too firm.

How does it compare with a foam mattress?

It is bouncier, sleeps cooler and holds its shape at the edges better than most foam beds. Foam contours more and isolates motion better, which matters for couples.

Does it need a box spring?

It works on a standard queen frame or foundation. A box spring or slatted base is typical for an innerspring mattress; check that the foundation supports the warranty.

Will it soften over time?

Innerspring mattresses usually soften as the comfort layers compress. Owners report some softening after several years, so rotate it regularly and use a mattress protector.