Infection - Yes, it has the organic / shadow tech hint, but good god this is a clunky as hell monster of the week episode that just doesn't work. It put a close friend off the series for life. He was unconvinced to start with, this episode put the nail squarely in the coffin.
Yes, I agree, that It is not a good episode, but at least it has a purpose in teaching the viewers about the concept of men and machine and how it works in the B5 universe.
The vindrizi, if I remember correctly, are those memory carrying spine symbionts? This episode serves the same purpose for the watchers as infection did for the pilots of the shadow vessels.
Grey 17 is missing does not work at all, true, but I vaguely remember that the A plot was good. So I forgive the bad B plot.
For me, TKO holds the title as the worst episode. I don't find Ivanovas plot very appealing. This, in my opinion, should have been the B plot to something that's got to do something with the overall story. The Fighting Plot does nothing at all (ok, the "you never watch your back"-line, but that's not really worth mentioning and the betrayal later stings just as much if we'd never hear that warning at all...
So for me, this one is an easy skip. Correct me if I forgot something of significance in Ivanovas plot.