I already bought one for my gaming PC but I'm thinking about adding it to the list of hardware for a new NAS. Are they to be avoided?
www.asus.com

Hyper M.2 x16 Card V2|Bundkort|ASUS Danmark
ASUS offers different kinds of motherboard accessories including Thunderbolt™ expansion cards, M.2 add-on cards, and fan extension cards give DIY PC users better choices when it comes to building their perfect workstation or gaming rig.