I used the 6 month 0 payment and 0 interest deal on my '04 with the Yamaha card (=Household Finance). The bill would come each month, showing Zero $ due. I chose to make extra payments anyway during that time and they noted everything perfectly each time. The billing statements were spot on. Balance due, payment due, etc. At the end of 6 months, I paid it off. I called them and they sent a letter which was sufficient for Idaho DMV, then my state issued a real title.
It went smooth for me, but if you have a big balance dangling on your bike, go to your credit union or local bank you like, refinance it SOON. Get a new loan and have them pay off the Yamaha / Household loan. Better to have the lienholder in your state and neighborhood, IMO. You can usually get some killer rates and have a local person to deal with. You could get stuck with some high interest payments if you stay with the Yamaha financing, as it it about the same as a credit card--high rates if you don't pay it off each month.