I picked up the white one today from work, I saw the black, and wasn't even slightly tempted IMO it looked pretty tacky and nowhere near as classy as the white..
But yes you can transfer your friend codes heres how!
If you still have your old phat DS, and you have Mario Kart, then you don't need a new friend code. Set your DS-Lite to download play, put in Mario Kart in your phat DS, set it to transfer WFC ID, and the DS will do the rest, it will delete the WFC ID from your phat DS and transfer it to your DS-Lite --- you will retain all the friend codes for your Animal Crossing, Mario Kart, Tetris DS, Metroid Prime Hunters (I hope I haven't left out anything).
Bought the white one too, PSP taught me not to get a shiny black console anymore (fingerprints fiest).
Found the display to be amazingly bright and front buttons to be shitty as hell compared to the original DS. The sound volume is kinda lower too with my earbuds.
edit: amazing->amazingly bright
just tried Castlevania... gotta find how to lower the brightness
reedit: found, and i was not even at the max... amazingly bright indeed