If you're particular favorite flavor of the Android OS is on the more custom side, there are many variable options that one can choose from when flashing a Custom ROM. Cyanogenmod is an obvious choice and definitely one of the most popular. Some good news in this department for owners of the Samsung Galaxy Tab Pro 8.4 is that Cyanogenmod is now officially supporting the device, which means you can get started on rooting and flashing whenever you have the time. We only recommend this of course if you aren't fond of Samsung's Touchwiz UI that comes onboard, but if you don't mind letting that go and navigating to a more open route with less clutter, the the team at Cyanogen has released official nightly builds for the tablet as of now.
We realize that rooting and flashing custom ROMs won't be for everyone, but it's great to see some support for this ROM coming to more devices. It may have been only a matter of time of course before the Samsung Pro devices received such attention. If you have and use a Samsung Galaxy Tab Pro 8.4 then go ahead and prepare yourself to move forward. Obvious things to note, are that you should be aware of how to root your device and follow all instructions and steps if you haven't previously acquainted yourself with the process, that is assuming your device isn't already rooted too of course. If that first step is already done, we'll assume you're most likely up to date on backing up anything you want saved before you move onto flashing which would result in a device wipe of the data onboard.
Other things that are worth mentioning is that if this is your first time ever attempting to use a nightly ROM, definitely expect some bugs, but since these are also nightly releases the bugs usually get fixed up quickly as a new build comes out generally every day, until they reach an M status release build which is now the most stable. You can find the download link for the ROM file here, and you can most likely find all your rooting instruction needs at XDA if your device is still stock. Happy Flashing!