I bought one new from AbuDhabi in December 2009 and its honestly its just like their tag line, the best or nothing ..its like a yacht on wheels, it simply glides on the roads.
Its best thing in its class on wheels for a luxurious drive and everyother emotion that comes with it. Of course I treat her well and make sure all the services are done on time and I usually do mine at the dealer itself.
So if you ask me is it dependable for the last 5 years and 80K kms driven...YES
Things to look out for:
Tires cost me a bomb the first time I changed it with the recommended Continental SPort, but for the next change I got great quality korean ones and its been great for 1.5 years and that at a fraction of the cost.
It isnt all roses though, i did present me with a rather big issue once in the last 5 years, but I was told many times thats its a one in a million chance that I get that kind of an issue especially with an S class.
Anyway theres one advice I would give anyone getting a luxury car..take the extended warranty, if you dont get it with the car. This is what saved me a lot of money. It covers all the major works and it saved me almost 50K and it cost me 12k for 5 years for the warranty contract.
Good luck and save up for it. Its worth it.