Jono, Vivek, Quentin, Hosermage, and Terry?
Couple of thoughts...freeform here after a long day cleaning bathrooms...do not ask!
I remember the WB thread concerning the A850 with Douglas...yes you have it right - really does work if you pay attention to light color and intent. Love your yellow man...would love to spend mornings in your kitchen's light...sidling up to an AGA. Ha! now you know my biases.
The NEX cameras did not inherit the wonderful skin tones nor color palate of the A850/900s...I would love to drop that chip and workflow into a NEX 7.
Magenta and Red is a common problem with adapted lenses from Leica and VC...not so much with Zeiss ZF2's ... and Terry is dead on...the LR 4 local adjustments are very helpful. Otherwise a Color Balance Layer in PS with mask to paint over areas that are way off.
Hosermage...WB has nothing to do with the magenta areas from trees and sky...overblown areas tend to go magenta and if you are not into HDR (personally I detest it!) you need to use a mask to tone down those areas or try the adjustments in LR/PS. The 5N does fabulously with wide angle lenses whereas the NEX 7 has HUGE problems with lens color cast on Leica and VC lenses...here the local gradient in LR or Capture Raw will help...Corner Fix seems to miss a bit of the cast ... compared to C1 or Phocus corrections.
I cannot find words to express how good LR4 is - even in Beta. I have moved 6000 files over to LR4 and hope that the final will be an easy transition...if not I have already seen enough difference to make it a priority. Still moving to PS for final edits but what a nice program.
Seems like there is an edge to every interchange recently...maybe my week in Southern California made me a bit more sensitive to things but guys...this is a very congenial site...lets give each other some slack...I know for a fact that NO ONE IS OUT TO EAT YOUR LUNCH. Just saying.....