I have run several Mercedes before purchasing a used R-Class from a Mercedes-Benz dealer in the UK in 2008.
The R-Class has by far and away the best front seat accommodation in any vehicle I have previously owned. There is an enormous amount of space in the foot wells and space for your knees to spread out on a long trip. The front seats are very adjustable, soft and comfortable for long journeys, and the driver's position is supremely relaxed and offers a commanding view of the road and a great view of your surroundings.
With an optional panoramic roof, the cabin is very light and offers an impression of space for anyone traveling in the car, which is especially pleasing when covered long distances. Only the third back row of seats is slightly cramped for legroom and a little short on headroom for six foot adults. If you don't expect to carry seven people and their luggage, you are very unlikely to be disappointed with cabin space and practicality. It has massive space to offer five adults and holiday luggage, and folding all the seats down in the rear offers a huge flat load space.
The standard level of trim is perhaps a little basic for the price, however I found and purchased an ex Mercedes-Benz UK demonstrator vehicle, which had been well specified with a huge saving on list price, which was just three months old and that came with some fantastic extras, which I could not have justified (or afforded) on a brand new car myself.
Fuel economy is not a strong point as I have averaged about 27.4 mpg according to the computer since I have owned the car, but at the end of the day, a 4x4 7str full sized vehicle like an R-Class is not really designed or purchased for outright economy. The tyre wear has been great as I still have 2mm on front and 4mm on rear tyres. So far I have need just one service, which cost £265.
Although I have been careful with my car, the interior still looks brand new every time it has been cleaned, and it has worn daily use very well.
The 4x4 aspect of the chassis means the car always feels safe, especially at motorway speeds on wet roads, and even in very rare snow the car has always taken me from A to B safely, quietly and in great comfort.