I'm a fan of CF, but as others have said, looks a bit weird without the front cover.
But congrats on your purchase

I think the main thing with air filters is it increases responce more than increasing power. I doubt you'll feel any noticable power difference, but responce I reckon you will.
It is a little on the expensive side, but hey, its for a merc, and the top of the range one (for the C class!), so:
1) they can't charge next to nothing or else we'll question the quality of it
2) they need to put alot of effort since the stock one already does so well, so to make it better needs alot of R&D and thats where the money goes!
At least thats my view on it