Yes, I get surprisingly good inductive coupling - on the bench I've had 90% coupling efficiency, driving the primary coil with a signal generator at 3 MHz.
The inductance of the coil I'm using was calculated using an online tool, not measured - maybe I put a number in wrong and it should be 100 nH, but it is a very tiny coil and 10 nH seemed intuitively correct to me. 3 MHz really is the optimal frequency (well, ok, it's really closer to 2.9 MHz) as tested with an RF sig gen and oscilloscope on the secondary coil.