I've been out shooting with my KIEV-88 (pre-CM version) these past two weekends. Mainly to test the Aki-Asahi anti-reflection flock set I've installed.
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VEGA-12V 90mm f/2.8 and Rollei Superpan 200
Biggest problem I've had with it was the slow speeds sticking. The airbrake wasn't turning freely due to a bent frame holding it. And another was the L-shaped part going into the stack of gears being bent out of shape.
Both were relatively easy to fix, but you have to know what you're looking for.
Latest problem was after installing the flock set the mirror was slow on the first part of the flipping-up. I installed the rear most strip too far forward on the light baffle. The adhesive layer of the strip was sticking to the underside of the mirror after a day.
Light leaks in the magazines have been mentioned. Make sure you always pull out the darkslide completely. Leaving it sticking out partially allows light to get past the edges of the slide.
I paid a €100 for a set with a VEGA-12V lens, two magazines, TTL-prism and some extension tubes, neatly packed away in a hard case.
Definitely not disappointed with it though. But yeah, as suggested, if you're looking for a reliable 6x6 SLR, you will want to look elsewhere