As far as consumers reports goes, the current 08 reliability data places Mercedes Benz just ahead of Ford but below Kia in reliability. It still has a way to go before it catches up with the benchmark set by Toyota and Honda in quality.
No, you have all season tires. Winter tires now have a snow flake symbol. At any rate, regardless of what tires you are using you are responsible for whatever damage you do if you hit someone. Your insurance pays.