A lot of people like to cast the ARMs as being evil and anyone who used one as being stupid. I think the ARMs have their place and I can see how it would work out for some buyers during some markets.
If climbing the property ladder or leaving your options open to job transfers are part of your priorities then planning ahead is just that – looking forward. You might have better things to do with the cash during the interim.
But if the reason for using the ARM is because you couldn’t afford the purchase and you are fantasizing about values continuing to increase into perpetuity then the ARM was a horrible mistake and you’re an idiot.