Bulbs warm up pretty quick. The STi HID's seems to warm up almost instantly, while my TSX took 5-10 seconds. I'd say these are right in the middle, as Drift Motion mentioned.
The first couple times using the bulbs, there was some definite color change, to white light, from the bulbs "breaking in" is my guess. No flickering, no issues.
The squirrel finder light scatter is definitely evident to me, so I need to resolve that. My gf and others who have been in the car at night don't seem to be bothered or notice it.