$58 a month on 150 points is actually a little bit on the high side. If you are buying SSR (which I assume you are), it will be about $48 a month for the current year.
The percentages off are a bit confusing because Disney is giving "incentives" of so much off each purchase, but they apply this amount to your down payment. I think the current incentive is $8.00 a point, so for 150 points, you will get an additional $1200 towards your purchase price. This isn't quite 10%, so I assume that is where the numbers of 11% and others have come from. We put down 20% total when the incentives were added into our down payment (but the incentives were $10 at that time, so it was actually 10% of our down payment - the other 10% we paid in cash).
I decided to lock in 10 years just in case something came up and I couldn't follow my "pay it off in 2 year" plan. Many people here will tell you NOT to buy
DVC if you can't pay cash, but I am not one of those. I think that by the time I saved enough to pay cash, I would have lost 2 years of vacations and its worth a bit of interest to me to get those couple of years with my children at WDW. It might have even turned out to be more years of vacations since something always seems to come up in life. I am not a person that can wait to purchase my next car until I had all cash to purchase it either, but I DO pay things off as quickly as possible or get the lowest possible interest rates when possible.
If we didn't finance, we probably still would be sitting on the fence 10 years from now.