I just wanted to point out one additional piece of information. While ing mortgages are indeed ARMS, there are two types of mortgages that they offer.
The "Easy Orange" is the option being discussed in the original post. That option does in fact have the balance of the loan due in a balloon payment at the end of the five years.
The other option is called the "Orange Mortgage". This option has either a 5 or 7 year ARM with the fixed rate for this period of time. However, the mortgage has an amortization period of 30 years (360 months). After the initial 5 or 7 year period is up, the rate does adjust to the current rate, however, the balance does not become due. Also there are limits in place as to how much the rate can go up. In other words, the rate cannot jump from say 4.5% to 8% or more because of the limits. At this time you can look for a new loan at another bank if you so choose.
During the 5 or 7 years period of your ARM, you are also able to lock in at a lower rate if the rate does indeed go down. There is a fee for this, however, substantially lower than at a normal brick and mortar bank. Also, when you reset the rate, it does not reset the loan term back to 30 years. So you are indeed paying it down quicker.
This post in not intended to try to convince anyone to use ing for their mortgage

. I just wanted to point out that in certain circumstances people may want a lower rate period in order to help pay down the principal, etc.
I have been reading on the Dis for over 11 years now. I finally came out of lurking....