One thing so far is that in low light high contrast situations there can be a lot of flare around bright lights. Not terribly bad with correct exposure but not perfect either besides it is raining out there!
High ISO is very good. Here is an ISO 6400 night street image in the rain shot at -2 ev exposure compensation 1/75 @ f/2.8. WARNING!!!! Hand held boring test photos. Shot RAW Adobe LightRoom 4 beta default processing with no noise reduction and no sharpening.
And a 100% Crop (ISO 6400 -2 E.V.)
Edited by BillM, 01 March 2012 - 01:33 .