I think it also has to do with the varying broadcasters and potential copyright implications; without going into further detail on the subject, UK has a more narrow and streamlined broadcasting system, whereas here in America, plenty of options and legal issues prevent 'cool' dvr functions like this (think also ps3 dvr capabilities).
As far as input lag, I am staying far away from samsungs due to their lag... From what I have read, the 810 has minimal lag, and due to user reviews and the early reviews out so far, the 810 jumped to the top of my list! I think the samsungs are also STILL using the same small capacitors resulting in power failure issues and relay switch issues. This is the reason, along with input lag, why I returned the ln46b640 and then the ln46b750 I bought last year (been on the hunt for a replacement since). The 810 would certainly get my vote for reliability, quality (less lipsyncing issues due to their processing versus samsungs AMP), and input lag.