When rates were low it really didn't make sense, unless you planned to be paid off before adjustments. If you have poor or average credit an ARM can get you a lower rate and the mortgage will boost your score to refinance to a fixed rate you couldn't get before. ARMs have max adjustments as well, so if you anticipate rates increasing more than that, you can get a lower rate than available at the time and in the future.

Bridge loans are less popular now, so you could get an ARM or interest only ARM on a new house and refinance later after selling your old house.