I posted this in the samsung 8550/9000 thread recently, but I figured I would post it here too, since I have a feeling people who own this TV will likely have it hooked it to an HTPC. So you can maybe learn from my experiences...
so, for anyone who wishes to use their 4K TV with an HTPC, I have done some extensive testing over the last few weeks with it.
It's been extremely frustrating, because I could never get the PQ or the motion handling (judder performance) to match my stand-alone cable box & blu-ray player. To top it off, there is literally no information on how to best optimize HTPC performance for 4K TVs. If you try to follow the current guides for 1080p sets, you will be very dissapointed with the performance.
Today I found the key to make it all work (and it sounds stupid simple, but it also somewhat defies logic). You have to run xbmc (or your favorite HTPC app) at native 4K resolution at 60 Hz for optimal video performance.
It defies logic, because for every other device, such as with receivers or oppos & the like, you are better off having the TV do all the upscaling, and disabling upscaling in the device, leaving the source content at it's native resolution. But this doesn't apply to HTPCs. I don't know why... I wish someone could come up with a technical explanation for it. But if you watch TV at 4K @ 60 Hz on your HTPC, the performance & PQ will be identical to a cable box. If you run it at 1080p or some other variant, you'll get bad judder, ghosting, and lower PQ.
Here's a thread I did on this subject in the HTPC section
Live TV PQ on my HTPC is inferior to PQ on my cable box
I don't think many other 8550/9000 owners are using a cablecard + hdhomerun setup for live TV like I am, but if you ever plan to, you'll find this info valuable.