I have flashme installed on my DS Lite for a few reasons. One being that I like the fact that the health and safety screens are removed, second being that the DS *can* be restored if ever hit by a trojan, and third: It is a requirement if you use the DS-Link, which happens to be my slot1 solution of choice.
Now, I realize that the mk4-mini can be used and then swapped with the DS-Link, but that is just not as smooth as using flashme.....so for me not an option. And the trojan ordeal...yeah...maybe it only hit a handful of people. Maybe it'll never happen again. Maybe? At least I know *definitely* that it will at least never happen to my device!
EDIT: BTW, you CAN unflash a DS Lite using the DS-Link. I posted more about this over at SCdev. You basically need a DS-Link, the software that backs up firmware from their website, and a way to boot the DS-Link on an unflashed device (ie: MK4-Mini, MK4-Key or SCDS with MK4 dump). Back up the unflashed firmware, restore it on a flashed DS Lite. Works a charm...I have done it successfully as well as two mods over at scdev.