We've got porcelain tiles with under-floor heating in our kitchen/diner which has proved to be very satisfactory. The porcelain itself is cold if you turn off the under-floor heating system, however, once you turn it on it becomes pleasantly warm, the heat distributes rather evenly.
We do have radiators because we already had them, but we don't need them much since the under-floor heating system is working in there. It was my first experience with porcelain tiles and I would recommend them, particularly in open-plan rooms."