Apostrophes or is it apostrophe's?

[indysteel]

I knew I'd make a mistake in that post... but I think most traditionalists would argue that it's really Ph.D.s

Or is it Ph.Ds.?

Beats me. In all fairness, there is some dispute as to whether certain acronyms, e.g., those with periods, and usages like "the 1980s" should take an apostrophe. I, personally, prefer them without because it seems more consistent with the other rules on apostrophe use. Whichever rule you follow, just be consistent in any given communication.