Loads of issues with my 2.3 Core i7
Running hdmi to dvi monitor and colour and sharpness fine. Do get the 'tv noise/snow' issue and have to reboot my monitor or sleep my machine to fix it but that's just the tip of an annoying iceberg.
Bought it, powered it on. It refused point blank to talk to my apple wireless keyboard (new style one), yes it had been paired with my old mini but nothing worked so had to resort to a 15 year old usb logitech wireless kbd + dongle just to get to the desktop. Then it required another reboot and several pairing attempts before it finally sync'ed with my apple keyboard. All bluetooth fine since but a major pita during install/first boot.
Plug any storage into the firewire port and all of a sudden booting from external usb3 devices becomes a total nightmare. Seemingly almost random detection of bootable partitions, having to unplug and replug usb2/3 storage devices and a reboot (sometimes several) before it'll boot from the right drive. Thankfully it then sticks but this thing sometimes feels more unstable than a hackintosh. OS is now via a 64Gb sandforce sdd in a usb3 caddy, internal 1TB used for storage plus an additional 1TB raid0 firewire 800 hardware raid and a 2TB time capsule router/nas.
On the plus side have stuck 16Gb in it even after the issues and it kicks arse at serving Win and Lin desktop seamlessly with decent 3D support in all OS's. It 'feels' like a hardware kvm combo activated by a swipe of two fingers on my magic mouse or like using wine without the constant compatibility headaches in windows mode. OS X pisses over the competition for seamless triple OS X / Win / Lin integration.
My old machine:-
Mac Mini early 2006 CoreDuo 1.66Mhz (upgraded with a 2.16Mhz C2D) & 3Gb Ram
Running Mountain Lion 10.8.2
Firmware = Hacked Late 2006 firmware (early 2006 firmware tops out at 2Gb)
Bootloader = hacked boot.efi to allow booting a 64bit OSX from 32bit EFI (f. u. Apple)
Gfx drivers (the only 64bit ones compiled for intel gma (f. u. Apple)) 10.6.2 intel gma950 drivers - (f.u. Apple a newer GMA driver for my old mini would allow it to run Mountain Lion perfectly).
Wireless works fine once the drivers from 10.7.8 simply replace the 10.8.2 ones.
Internal sandforce 64Gb ssd
Performance when running Lion = Damn good, just gfx holding it back and not really enough memory for vm's. Compatibility with all usb2/3 and firewire devices I threw at it though even though heavily modified.
2.3 Core i7, 16GB ram
Running Mountain Lion 10.8.2
CPU Performance is astounding but the GPU really lacking already, roll on Thunderbolt gfx cards asap.
Compatibility with storage devices (and bluetooth annoyance) is truly horrid.
OSX I suspect is not the culprit here, it's just the damn firmware of this wee beastie that needs to be fixed asap. the bugs are damn annoying (I don't expect hackintosh like boot nightmares from Apple) and it's the worse out of box experience I've had of any Apple product I've bought.
Not a good sign, Apple get your S*** together.