Safe, until redNAND decided to pull off "?" on DS VC game in home menu and you're basically screwed.
redNAND is only good to dump NAND, nothing else. [Oh and for developers]
Still, i wouldn't use redNAND at all, it's barely useful and corrupts every 2-3 reboots.
I basically assumed RedNAND was for more advanced tweaking, so I didn't think it was worth me doing. I only play games and wanted some of the Eshop titles and DLC, so I think i'm good with Haxchi for now. Installed it earlier and it's working as expected, so i've got what I need I think.