What do you guys think about an Adjustable Mortgage Rate (ARM)?

For all you Adjustable Rate Mortgage skeptics… right now you can get a 5-year ARM at 2.50%. I know the biggest CON to this is that in 5 years, it may adjust to 6–10%. But what prevents me from just refinancing again at that time? Do we really think the economy is going to be “fixed” in 5 years and that 15, 20, or 30-year fixed rates are going to be that much higher, if any, than they are today? At this writing, a 30-year fixed is 4.125%.