I have a bunch of lovely old full frame K mount lenses (like the 50mm f1.2 and the 135mm f2.5) and the idea of using them in a proper mirrorless body (I have the K-01 and that's a hell of a brick) without the crop and an extra stop of light seems really interesting.
I've seen that there are Mitakon Lens Turbo that adapt Pentax K to Fuji X and Sony E mounts, so using my old lenses at full potential in a NEX 6 or a X-E1 seems like a dream come true, but I am afraid that the extra layer of optics can really degrade the image quality (mostly if it's a cheap made in China glass).
So, does anybody have experiences with focal distance reductors?
Is it much better the more expensive Metabones Speed Booster (although there are no K-mount versions yet) than the Mitakon Lens Turbo?
Would it be interesting to wait for a µ4:3 adapter (that are said to come out in the second half of 2013) and use my lenses in a GX-1 or an OM-D (the smaller the sensor, the greater f-stop boost, so the ISO noise differences are kind of compensated)?