Are there any downsides? What is there to gain aside from not needing a passcard? What all does it change?
- Gets rid of the Health and Saftey screen. - Adds a recovery system should your DS get bricked by a trojan etc. - Allows you to have an original cart in the DS while using a backup, which is useful for only Mario Kart as far as I know (i can use the hacked tracks, but use the game save form my original cart to keep my stats etc) There used to be more benefits of FlashMe, such as power consumption and space saving, but these became void with the introduction of the Passcard over the old PassMe/Passkey.
If you brick it while flashing you have some choices - Try and recover using te recovery function, I can't remember how to use this, so you need to look it up. Obviously this might not of installed when you brick it mid flash. - Get another DS and open them both up switch the dead bios with a new one and start FlashMe, then switch them back and run FlashMe, this should work apparently, though i've never tried it. - Use PPflash to recover the firmware, this needs soldering skills to solder acbe to the DS temporarily. - Buy a new DS and then take it back a day or so later saying it won't work ;-) If you follow the instructions posted on many websites on how to do it you shouldn't brick your DS anyway, i've done FlashMe on several DS and DS lite without any problems.
i bricked my lite and exchanged it since i was too lazy to hotswap the bios. so option four is best, its like brand new!!!