(I'm in the process of installing now, so I'll answer as many of these questions as I can. I will also update the OP with info from other users. If anything I state is untrue, please post and let me know.)
Can I take the update while rooted?
Yes! If you are on 4.2 and rooted but on STOCK RECOVERY, you can take the OTA and keep root.
Can I take the update with TWRP installed?
No! You will bootloop into recovery.
Is there an alternative/manual/TWRP method of installing?
Yes, see below post.
How am I supposed to update if I installed TWRP?
See below post, "README if you are currently on JB4.2.2"
Alternative method: "download flashify from the play store, backup twrp, then flash the recovery.img from OP. No pc needed & 100% pain free." Thank you to 86shelby. Then take the OTA.
Can I root the 4.4 version?
As of 8/26, yes! Stumproot works with the Bruteforce method. http://forum.xda-developers.com/show....php?t=2850906
Can I downgrade from 4.4 to 4.2?
If anyone else has questions they'd like posted, please let me know, and I'll put them in.