The New York Times Manual of Style and Usage (1999) agrees with Words into Type about the apostrophe, although about little else:
decades should usually be given in numerals: the 1990’s; the mid-1970’s; the 90’s. But when a decade begins a sentence it must be spelled out. [example omitted]; often that is reason enough to recast the sentence.
NY Times seems pretty reputable and they like the grocers’ apostrophe