I really don't see why there should be a problem with "used to," as in "I used to drive an Isetta, but now I have a Yugo."
Saying simply, "I drove an Isetta..." could imply a one-time occurrence.
"I formerly drove an Isetta..." conveys more formal, perhaps even pretentious, speech. OK, if that's what you intend. There are other constructions one could use that avoid the problems of either of these but why? "Used to" strikes me as perfectly acceptable in informal speech.
The two references to "used to" in my 1959-vintage Perrin's Writer's Guide and Index to English merely exhort one to avoid the misspelling "use to," but make no reproof against its usage in general. Indeed, I don't recall encountering any admontions prior to this.
As a side note, I decided to check Perrin on what used to be a minor pet peeve of mine, alright vs. all right. Here's what it says:
"All right is the spelling of both the adjectival phrase (He is all right) and the sentence adverb, meaning "yes, certainly" (All right, I'll come).
"Alright is a natural analogy with altogether and already but is found only in advertising, in unedited writings, and, rarely, in fiction. It will be worth watching to see if alright makes its way into general English. In the meantime, be on your guard."
Prophetic words indeed. As my personal vintage predates even that of Perrin, "alright" triggers a reflexive sense of semi-illiteracy whenever I come across it. Obviously, evolving usage has passed me by.
