If you have access to the attic and it's unfinished, check if there's a reflective layer above the coils. If not, that's easy to add and will make a big difference.
Not this is a _reflective_ layer, not just insulation. The thermodynamics of radiant heat systems involve photon transmission, not just gas convection. If it was installed by a general contractor they may not have understood this distinction and the need for aluminum couplers and metalized reflective insulation.
Thanks for that tip, I'll try it. I actually reasearched it a bit more, and see that it is possible to have in-ceiling radiant that isn't crap, it's just that mine is crap. Supposedly it responds faster than forced air, but mine takes about an hour before I feel its effects. Also one room has 12' ceilings, which is stupid.