I have read that most cars come with bulbs rated at around 4500K, however the blueish tint often seen is down to the projectors and not entirely the bulb itself. My personal view is that having had 6000k Philips bulbs in the past (albeit the wrong fitment), the colour these bulbs give through the Supra UK lights is superb makes the car look great in the dark, plus when cars see you coming they just move out of the way! (probably thinking you're the police).
My kit (Philips LVQ-212-L300 ballasts with Bosch rebased 9006 bulbs) from an eBay seller (with excellent 100% feedback) is arriving today, and I will post up a full comprehensive review once I've had it fitted - as others have mentioned this is what we need as there are so many kits out there and the results are variable.
All this said, HID is extremely popular and is only just begining to catch on here. I wouldn't be surprised if we saw the prices of these kits coming down, and there isn't any reason why we shouldn't be seeing good and cheap kits made by the Chinese, but of course it's all down to people trying and testing before one can say for sure.