Samsung might be giving lip service to the new Note 5, but it's clear that the company (and a considerable portion of buyers) sees the more swanky Galaxy S6 Edge+ as the flagship device. Now those who've paid the premium for the curvy phone can use the most popular custom recovery out there: Team Win Recovery Project. The developers have posted an official build of TWRP for the GS6E+ to the website.
The website lists this recovery for the GSM version of the phone, so presumably it will work with the standard international version and GSM carrier variants that don't lock down the bootloader (so... everyone except AT&T). CDMA carriers like Sprint are so far unsupported, but that's not unusual - expect unlocked versions of those phones to get a TWRP build, either from the official developers or others working from the open-source code, soon enough.
TWRP will allow power users to flash custom ROMs and other modifications to their phones, as well as perform practical actions like software backups and partition wipes. Of course, the unique double-curved screen and Samsung's customized software on the Galaxy S6 Edge+ might make a custom ROM less attractive for this particular hardware. Remember, any modifications to the stock build (even if it's just root) will prevent over-the-air updates from being flashed.