I really have to wonder what can you use 10G for? I have 500M down from my ISP, and it is faster than I can imagine ever needing, unless I get into data-hoarding 8k movies.

For most people, 500M is probably fine. But once you have a few family members, each streaming 4K movies to their devices, and a parent that needs a video call to work seamlessly, you start to see the benefits.

10G is probably overkill, but it's also future proofing. The way things are going, loading the NYtimes will require 10G just for the advertising alone...

True, I don't really feel limited by my existing 500Mbps down, but knowing I'll be having 2500Mbps up/down soon means I want to have the infra to handle it.

Basing things on 2.5GbE would certainly have been cheaper but some things don't support it (they either do 1GbE or 10G SFP+) so settling on 10G where possible made more sense to me. My future ISP also has a 5Gbps up/down option, but even I can't justify that right now.

My wife and kid just want their phones/laptops to work, and to be able to stream stuff to watch, they don't care about the underlying speed.

Having a faster network may make some of my work related things run a bit quicker. A few times a day I'll need to pull something big down (either an ISO or a bunch of docker images) and that can take up to 2 minutes with 500Mbps down. Having those take a fifth of that time will make it seem less of a roadblock to doing work. 2 minutes meant I went and got a cup of coffee and often got more distracted, 30 seconds should keep me at my desk and focused on what I was doing. That's not a big enough reason to justify it on its own obviously.

I also want to do offsite backups with/for various family members, so something better than 75Mbps up is going to be a huge boost. Getting 1Gbps+ out will be huge (assuming whatever is at the other end can support that).

I don't do any kind of data hoarding, I think I've got something under 4TB of data that I actually care about, and most of that are family photos/videos.

Deep down it's mostly because I'm a networking geek so it's fun to play with some new kit and make blinkenlights.

My homelab has a 10G fabric (switched) for NFS, iSCSI, NVMe-OF, etc. and a 25G fabric (a mix of back-to-back and switched) for clustering (Ceph, DRDB, ZFS replication, migrating VMs).

I spun up some iSCSI-backed SQL Server a few months ago and 10G couldn't keep up with the workload, so I dropped in a pair of 100G ConnectX-4 cards with iSER (iSCSI Extensions for RDMA) support for that particular use-case.

Just because your uplink is less than 10G doesn't mean the rest of your network can't be a bit more capable. :)

It's less "what new thing can you do" and more "what things involve noticeably waiting, how long is the waiting, and what else is impacted". E.g. updating a game on Steam practically takes slightly under half the time for me (1.2 Gbps actual rate) and has absolutely 0 impact to any other traffic in the house. If it was 10x the price to get 10x the bandwidth I wouldn't bother but it was actually about the same as my old cable modem plan.