University of Virginia, among its many traditions, has its instructors and professors all go by Ms or Mr whether they have a PhD or not – it’s all about Thos Jefferson’s abhorence of titles. I had professors there who would actually scold you if you called them Dr or Professor.
In my current program, we do not offer tenure even though we do have full-time faculty and certainly promotion (mine is what they call, I think, a ‘bridge program’ as our students can finish at the AA degree, or go on to the main campus to complete their Bachelors), but all PhD’d faculty in the program are recognised as Assistant, Associate, or Full Professor officially by the program’s guidelines and the main university’s criteria. Non-PhDs are instructors. The pay scale reflects this as well – as a new Assistant Professor I was paid more than a colleague who’d been there as a full-time, published instructor since the early '80s.
My students, especially the freshmen, frequently call me Miss or Ms (and the occasional ‘Mrs’ but I do correct them that Mrs Boods is my mother, but I’d be more than happy to turn over their marking and grades to her if they’d like); I, like Dr Evil mentioned above, remind them that I didn’t spend years in evil grad school to be called Miss or Ms. (Freshmen have also asked me if they can call me by my first name – sure, as long as they remember that my first name is ‘Doctor’ or ‘Professor.’ I have no problems with my grad students, however, calling me by my first name, especially as our primary contact is through a teaching-training program I’m a part of.)
I did have correspondence from colleagues at a German university for a while, so it was entertaining to be addressed as Frau Professor Doktor.
I’m an assistant professor now, and as such in the US can be addressed as Professor or Doctor Boods. But next autumn, I will be a lecturer in the UK, so I will just be Doctor Boods – Professor is an entirely different animal, usually venerable, highly-published, senior members of their departments (who might get quite cross with you if you slip up and call them Doctor instead of Professor.)
Then there’s that whole thing in the UK where you spend ages qualifying to be a medical doctor, and get called that until you get promoted to a higher position, and become Mr/Mrs/Ms! At least this is what about a thousand episodes of Casualty and Holby City have taught me over the years (they’ve also taught me that the minute you have to go in for surgery, even if it’s just for a hangnail, you’re dead. Unless you’re part of the main ensemble – then you can be up and about a day or two after major brain surgery/organ transplant/point-blank gunshot wound to the chest, etc. Neat!)