I did just last week.
Traveling between Houston and San Antonio I had my TPMS light click on while traveling at 80 mph (75 MPH limit), switched to the TPMS section on the dash and saw the front passenger tire pressure dropping. Pulled off and put on the spare, drove 20 miles at 50 MPH to a tire place.
But I agree, I have seen a vehicle with 2 temp spares on it (where the heck did they get the 2nd one?).
Interesting topic, I just got an '04 Sonata for my son and the temp spare is the original. I am debating getting a steel rim and a full size spare, would probably be cheaper than just an actual temp spare replacement.