I read somewhere, and maybe someone else can speak more definitively, that the servo circuit within the SL motor is constantly hunting for the proper rpm. While looking at the strobe it appears to be visually stable but the motor is continuously compensating.
I believe that's a widespread myth, and am pretty sure I even read it in Stereophile once. However, I've never seen any evidence that it's true, such as measured speed or pitch variations. Some people feel that the SL12x0 series has an upper midrange glare or resonance, and since the servo operates at 3500 Hz, some audio journalists *theorized* that the servo frequency caused the glare, but then passed it on as fact.
I've read on the KABUSA.com site that this is false, and he has the 'scope captures to prove it. In my personal experience with my SL1210 M5G (and AT150MLX for that matter), I set about to neutralize all resonances and vibration I could find. There *was* a persistent subtle glare in the upper midrange; when I flicked the tonearm with my fingernail it seemed to ring at the same pitch. The tonearm is an undamped aluminum tube, which by its nature is very resonant. I wrapped the tonearm in inexpensive lightweight Teflon pipe thread tape and the resonant peak disappeared.
Most of the complaints about the Technics lack of clarity can be readily and cheaply addressed with damping and vibration control. I upgraded the headshell to a pretty inert LPGear ZuPreme, installed KAB's fluid damper, wrapped the tonearm, swapped in a sorbothane platter mat, replaced the stock feet with brass cones situated on inverted Vibrapod cones sitting on Vibrapod isolators sitting on a 3.5" thick heavy butcher block cutting board isolated by some silicone gel pads. It sounds convoluted but cosmetically it actually looks OK and every tweak I mentioned incrementally improved clarity, musicality, lowered noise floor, improved dynamics, etc.
Yes, the Technics has some resonant peaks and some clarity problems out of the box, but they have nothing to do with the servo frequency and are inexpensively neutralized.