Has anyone had trouble with speed on their tt

Mosin You might be onto something about the platter being so important to speed control.

Google cog free , Ironless rotor , encoder with absolute Position,,, http://www.aeroflex.com/ams/motion/datasheets/motion-motors-zerocogging.pdf

The OP suggests that there was an actual malfunction that was speed related.

I would get some good days and then the temperamental thing would drift or even radically switch speeds ending my listening session

Two areas of difficulty here that can cause intermittent speed problems: the speed selector switch, which might need cleaning, also if the 'table uses any kind of servos to control motor speed, there are often potentiometers that are used to set the range. If they develop corrosion it can result in intermittent behavior. A simple cleaning (using a $5.00 can of contact cleaner from Radio Shack) can correct the problem in either case.

Some turntables do not have accessible servo circuitry outside of the motor, in which case the motor itself will have to be replaced.

In belt drive machines if the belt is perishing, it can settle at the wrong spot on the motor shaft, causing the 'table to be off speed. In some cases the motor shaft angle can be adjusted to allow the belt to set itself to the correct position on the shaft; if the adjustment is off this may cause the belt to have difficulties doing so.