We have had generally good experiences with the Mercedes dealer in Salisbury.
Never any argument on warranty work, both new car and Mercedes used car warranty. We have had 5 cars from them since 1999.
Possibly the most extreme was a total respray this year on a Feb 2011 car. I understand that Mercedes has an issue with Fire Opal Red applied to certain German built cars between September 2010 and June 2011. The etch primer applied to steel panels slowly reacts with the primer and the result is a separation of the clear coat from the colour coat. The solution is to rub down to bare meta, re-spray with 4 coats of paint, supplied by MB.....plus about £5000 labour.
I also understand that any car re-sprayed will not be re-sold by Mercedes as a used car, but are sold at auction. This makes me wonder how confident they are about the durability of the re-spray.
So, on the basis of my local dealer I'd buy a MB from them. Unfortunately at the moment there isn't a model in the range that I'd actually want to buy, though we will look at the new E Coupe when it comes out next year.