In short, on the positive side: great optics quality, even better coatings, hardly any chromatic aberration (probably some minimal false color was simply atmospheric dispersion at 300X+ mag.), the modular design is a plus!
On the not so positive side I would love a compression ring (but I guess its too much asking at this price point) and also there is some vignetting and loss of fieldstop clarity. Would I buy it again? for being a reasonably priced, modular, with great coatings and performance with short focal length barlow definitely yes!
Honestly, its 4.5/5 only because of the vignetting.