The people in Singapore have already gotten their hands on the 5Dmk3 as of yesterday Mar 16. (And most shops have already sold out their first batch last night)
I personally got hold of mine yesterday.
Was using the 60D before and i must say the mk3 is leaps and bounds better. The grip is nice though maybe too big for some small asian hands like mine.. The AF is very fast and accurate, as compared to the mk2.
But ultimately the reason i bought this camera was the ISO capabilities.
Unfortunately it is only really good at JPG. RAW ISO is only useable up to ISO3200 and maybe 6400 is you really have to.
JPG however, on it's default standard setting is highly useable up to 12800. Even at 25600 it's better than RAW at 6400.
I barely got the camera for 24hrs so i'm still exploring all the features, especially all the AI Servo tracking settings, there's just too many to understand in 1 day.
In the meantime, here's just a sample of out of camera JPG taken at F5.6 at ISO12800 of myself (pardon the ugly face)