My reports on my 27" iMac delivered to Sydney, Australia.
I have managed to use it for about 6 hours so far. I'll tell you it is beautiful, way lighter than I expected, and the screen is lovely and bright. I have noticed a very slight yellow tinge towards the bottom of the screen, however it is only very slight (I tend to be very particular about these things), and after some use I'm not really noticing it any more. I tested for image retention, at about 90% brightness setting, and have not seen any as of yet. Also have not seen any bleeding of backlight, and brightness is quite uniform across the screen.
The thing is blazingly fast with the 1TB Fusion drive. It is also completely silent, although once I have all my audio stuff setup it will start to get pushed so we'll see what difference that makes.
I have also installed an external MOTU Track16 audio interface. This interface works wonderfully with the iMac, and I had no issues installing it at all. It can work over USB3 but I opted for a Thunderbolt to Firewire cable, and connect it via Firewire... This all works great. The Track16 can be controlled on my iPad using TouchOSC... A brilliant experience.
I have also hooked the iMac up to my Samsung HDTV via a mini-displayport to HDMI adapter. This works great also, no issues whatsoever.
Apple TV mirroring works great too for those interested in this.
I am awaiting delivery of 32GB of G-Skill MAC ram to install, and am also awaiting delivery of a Promise Pegasus R4 4TB RAID external drive, these should both arrive on Monday and I'll report back on them too.
Downloaded and installed Logic Pro via the App Store, painless. Am waiting until my external drive arrives before I install all my plugins and sample libaries etc. With this new 10.8.3 update apparently some issues people were seeing with plugins causing logic not to respond should be resolved. I will report if I experience any problems setting up all this.
Overall, I'm very happy with the iMac, but if anything crops up, I'll be sure to let you guys know.
Just a note, mine was assembled in Shanghai.