Traditional induction heating is generally not cost effective for heating complex, variable geometry, but some new types of induction heating can effectively work like a very low frequency microwave... with the induction heating power supply tuning itself to the load that is inserted. Given the high power and a bit of saturation time, a piece can be heated without gradients... or if desired, selectively heated with an electromagnetic wand. Some companies sell power supplies that allow the user to wind their own coils to suit any geometry. iTherm Technologies - Revolutionizing Induction Heating
As far as the efficiency goes, it is more efficient than gas, hands down. If there is no load present in the coil's field, there is little loss of energy (as there is nothing to heat) and the only energy disipated is from the coil and power supply switches.
Industrial heating recently published an article I wrote on such systems... Embedded High-Power-Density Heating - Feature Article - Industrial Heating Not exacty what was described above, but the basic technology is the same.