Lots of the mini guys rave about these . From what I've heard their a good value product with decent quality to them . I have know idea what they will be like on a merc though .
They are the cheaper brand of KW and made in the same factory.
I'm not so sure about them on the heavier cars.
I had them on a Leon and they were very crashy over undulating roads.
A decent spring set may be another option for you, if you don't want to pay top whack for KW's, Bilsteins etc...
I fitted H&R springs to mine and the ride is a little harsher but also better than before.
In my opinion (from using them on my track car) they're too soft for the track but a fairly good quality coilover. For a daily road user they are a good inbetween.
Personally if I wanted performance I'd go bc racing with adjustable dampers or kw.
I feel the longevity on a heavier Mercedes might not be so great though. I'd pay an extra couple of hundred for kw