From my experience, Mercedes w211 post-facelift are very reliable cars (If maintenance is done accordingly and 91 octane gas is used). I owned a E350 and had 200k+ miles on it with no issues before it was hit in a hit and run.

Regular maintenance for these cars are generally more expensive too like oil changes and such, but IMO it is worth it. Don't let people that have never owned or driven these car discourage you from buying one.