Hey Cujet, I concur with your assessment. After being inside handful of ST heads, I don't recommend them. Mine is working OK, but even my backup unit ended up having serious problems, beyond bearings and rectifiers. Some are pretty good and/or can be made so by an AVR on the mains (to avoid many of the Z winding issues), but it's more work than the cost savings are worth. I'd rather have a 3600 rpm head than mess with another ST.
I believe the problem with your microwave oven is the cheap AVR you have; it is NOT regulating to RMS voltage, which a well functioning Z winding does fairly well. This affects a large, low power factor load like a microwave and will result in low voltage. I ran into this the hard way, of course. I have the ability to switch out my AVR and go back to the direct harmonic excitation with dropping resistor, and that's how I deal with that kind of loads (like a friend's small MIG welder running on low amperage setting).
Brad-
The folks who have followed Gary's advice and gone with the Stamford have reported nothing but easy, trouble free operation. I highly recommend DES. No marketing/promotional bullshit (I have a severe allergy to it), incredible depth of knowledge and 1st rate support.
On flicker, the best you can do is heavy flywheels plus a small brushed head with a fast AVR off of mains to compensate for the rpm/voltage sag of compression stroke and voltage rise on power stroke. Larger heads can't be compensated as well electronically due to much larger rotor inductance and the resulting lag in response.
Lister put a flywheel on the SOM generator and big flywheels for good reason. I have measured the reduction in flicker on my custom AVR versus another forum members's SOM flywheel 6/1 who I sent my measurment/filter circuit. They both provide about the same reduction. I found that improvement is just enough to allow me to use the 8-250 watt heat lamps in my shop; 60 watt incandescent bulbs are unbearable. LED bulbs which have a switch mode power supply, regulating the LED current will not have problems with Listerflicker. They do generate significant power line EMI but that's your trade off. So listerflicker can be avoided as an issue if you are careful about LED bulb/lamp selection.
Best Wishes,
Bruce