I recently did the XenonDepot upgrade on my 2008 as well. Very bright - I like it a lot thus far. They advertise the color temp as something like 13.5kº so it is much brighter/blue-whiter than sun/daylight, which is somewhere about 9.5kº I think. You will definintely want to filter the Putco lights if you want a 'warmer' (yellower) color.
I agree that they fade on/off as smooth as the stock incandescants. Their brightness, in really dark times, makes the factory solar tint (rear 5 windows) almost clear when viewing from the exterior with the lights on. Amazing really.
Now that I've updated the domes and map lights, I definitely need to do the doors. Their stock output now appears way too weak and their yellow color are out of place now.
