Just got new Falken 512's installed on the MB today. Only one days driving to report, but here's my observations...
1. My installer found them easy to balance. A good sign!
2. So far, response seems decent (I'm back to the OE 15" wheels...) and tread squirm, despite their newness is not bad at all.
3. The MB is is not a good car to gauge tire noise as it transmits little tire noise regardless, but they seem as quiet as any other tire I've run.
Time will tell, of course, but so far, so good. Once I encounter some rain, I'll let you know about their wet-handling ability...