I did it... switched from an old athena temperature controller to an omron one... not too bad as long as you get the equivalent type controller (relay vs voltage outputs, and the correct voltage input)...
however, you'll have to figure out the settings for the new PID based ones... the factory defaults will probably not be correct for the interval time, deravitave, and process times. that was my biggest/hardest hurdle.
after they were set better, it worked really nicely.
for the belt speed control, just hook up a digital volt meter to the output of your controller... the more volts going to the motor, the faster the belt.