I backuped my 3ds and lumas then updated... I didn't loose CFW and everything seems fine, other than free**op taking a bit longer to load game description. I have not tried using homebrew yet so not sure if homebrew launcher needs updating (Probably does). Apparently 11.4 blocks Smealums newest exploit and is probably another security update. If you need CFW dont update!!! If you have CFW and you backup and updated lumas you should be free to go.