It seems like there are only a dozen or so of redNAND users left so if you run into any corruption or redNAND specific issues (like updating system firmware) then you are mostly on your own. With that said, I've been using the same RedNAND setup for 2 years now and have never experienced any oddities, glitches, crashes, or corruptions that I didn't anticipate*. I use redNAND for testing filesystem modifications and for online play. It allows me to keep my WiiU on 5.5.1 and not connected to any wifi networks (personal preference) and my redNAND updated to 5.5.3, always connected to wifi without any DNS blocking. I use redNAND predominantly when I want to update/buy/play games online.
There are two different groups of redNAND users, linked and un-linked. Those with linked redNANDs (like myself) can share 1 USB device between sysNAND and redNAND. This means I only have to install games once but I can play in either configuration with the same gamesave.
I believe the key to having a successful redNAND experience is a good quality SD card and never resettings your sysNAND or redNAND once it is setup. Anything you install on sysNAND (other than haxchi) should always be installed on a USB device not the NAND itself. This will provide you with a relatively clean system to make a new redNAND from IF your redNAND somehow gets corrupted. Personally, I think the corruption is associated to shoddy SD cards and older revisions of mocha.
*Some known redNAND limitations for a more gamer focused Wii U:
1. vWii doesn't work. You have to use the vWii from sysNAND. In my case, since I have wifi only connected to redNAND, I am unable to access wifi on my vWii (by choice of my configuration).
2. Updating redNAND can be a pain. Some people can update the redNAND system directly, but most seem to have to manually update using a modified wup installer (with tickets) or even SystemConfigTool.
3. Slightly slower than sysNAND which is most noticeable when returning from redNAND settings app to the main menu. Adds ~5 seconds. Elsewhere its negligible.
