Thanks gentlemen! This was my first outing with the lens.
I love the (wide) reach of this lens. No color cast problems and distortion is not to bad.
For now I think it is a great interior/architecture lens. I am going to try it in a museum soon.
Outside in the sun yesterday it was all a little to contrasty to my taste, so don't know yet. Colors were a bit harsh.
It has no crazy flare problems. The first picture is right against the sun. (BTW this is the Piece palace in The Haque)
Leica R-lenses were little disappointment, but it in the end it seems to be adapter issue. Haven't yet shoot primes with masked adapters, but results with Vario-Elmar-R 80-200 f/4 were as I would expected from Leica R. The problem with standard adapters (any of them and I have many) was that white sky (outside frame, even sun didn't have to be on that direction) caused very crappy contrast due to reflections from un-masked adapter.