I've recently refinanced the balloons on both the ML and SL I currently own. Both were financed by MBCC.
I refinanced the ML balloon after the 47-month term to keep the payments low, and because of the advantageous interests rates these days, was able to refinance the balloon with MBCC for a lower rate. My balloon was a bit lower than the value of the ML, but not much. My new payments are about $50/month lower too.
The SL was a different story. I purchased it used and took a steep interest rate hit as a result. Could barely swing the balloon option on that car, and even those payments are tough. Being older, the SL depreciation curve was much steeper than the ML, so I was into negative equity once I left the lot!
MBCC policy allowed us to refinance after 2 years, and the payment now is about $30/month higher. But the balloon is no more, and the interest rate is much lower!
The truth is, if I were to sell any of my MBs now, it wouldn't be a profitable option. I would only recommend this route for someone who wants to keep their cars for a long time...and I do!
What the balloon did was allow a working stiff like me to own a fleet of MBs that would normally be reserved for more affluent individuals...
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car