[DC81]

To flash the DS you would need a slot 1 passkey. To buy one would be about $20 (which kind of defeats the purpose of flashing it, since you now have a passkey), unless you have a friend that has a passkey that you can borrow to flash your DS. Plus, rather than paying $20 for a passkey, I would rather pay a little more for the R4DS which will allow me to play NDS games without flashing, and if I want to play GBA games from a slot 2 cart it will act as a passkey.

I have read the there are some negatives with flashing, one that I remember is decreased battery life (I don't know why, but it is what I read), plus the risk of "bricking" your DS if flashed incorrectly.