I read in a 1975 issue of TV Guide that apartment-house manager and upstairs neighbor was added to interact with Mary since Phyllis and Rhoda departed for their own show. Was this a Good or Bad addition?

We never really got the chance to find out:

- The apartment manager only appeared in 1 episode.
- Her neighbors, Paula (Penny Marshall) and Sally Jo (Mary Kay Place) only made a few appearances. Penny Marshall, of course, had to tend to her own series.

IMO, I couldn't warm up to any "substitute" Rhoda or Phyllis. The writers apparently felt similarly, or at least had their own reasons for deciding to focus on Mary's interaction with her co-workers.

Some have said this the point at which the show "jumped the shark", to which I say, "Nay. Not true!" I think it was consistently fine throughout. A change of direction in a TV show isn't always downward; in this case, I think it was a lateral move.

P.S. -
This is probably more than you wanted to hear, however I know someone would've mentioned it if I didn't.

It wasn't necessarily better or worse when Rhoda and Phyllis left.