Yes I have. I've tried Frontier on an A500, vanilla A1200, A1200 with Apollo 1240/25Mhz and Apollo 1240/40Mhz.
The increase in frame rate is quite substantial in each case. Obviously the 40Mhz '040 was the smoothest, but you will notice a significant increase in frame rate by increasing processing power. There are options in Frontier to alter the detail level to suit faster CPUs.