This may be the worst episode of ST. The script seems muddled, the science seems plausible initially (identical particles of matter and anti-matter do annihilate and produce radiation, however human bodies are not "particles") until we see Kirk in the anti-matter universe. The instant his skin made of matter contacted the anti-matter atmosphere there would have been a big bang... The acting by Robert Brown as the mad (matter) Lazarus was over the top by even my standards (I consider Shatner an excellent actor) although his sane twin was done much better. As for the pluses there was the lovely Janet MacLachlan as a Lt. in charge of the Dilithium Crystals. Her role does however seem almost as if it were inserted by the producers as an afterthought. But the sentiment behind it is very much appreciated (although it was already being "covered" by Nichelle Nichols - still never too much of a good thing).