I bought my first license (and server) in 2009, I believe. The first server I ordered was directly from Lime Technology in the US, and I had to explain to the customs office in Germany what the hell that thing was. 😀
The two biggest improvements, aside from changing the entire hardware, were the switch from ReiserFS and the ability to use VMs and Docker containers - what a fantastic improvement!
Currently, my server is running in a massive Lian Li PC-D8000B HPTX case, with an MSI H170M-A PRO motherboard, an Intel® Core™ i5-6400, 32 GB of RAM, various disks totaling 60TB, and a WinTV-quadHD DVB-C card. I prefer using smaller disks up to 6TB, as the overall system is quieter, and I believe these disks are more robust. I should reconsider that.
I enjoy recording TV shows (in Germany, we have excellent public broadcasting) and archiving podcasts. Likewise, the server serves as a "data hoard" and backup. I'm using the following Docker containers: tvheadend, Emby, Paperless-NGX, Syncthing, and, for the past year, Lobe-Chat.
I don't know much about ZFS; that's a topic I want to delve into in the future, but I'm not sure if it would offer any personal benefits for me. I'm very satisfied with XFS; everything is running optimally.
A big thank you to the UNRAID team, the OS is one of the few products I've been using daily for many, many years. There have been hardly any problems, and the utility is fantastic.