I love using it as a second screen when I’m out at a coffee shop. It works so seamlessly and I can throw Slack on there while I code, without looking like a complete weirdo
Sidecar works surprisingly well. With its latency and performance it’s barely distinguishable from a wired screen even running a HiDPI resolution.
If you want, it's possible to wire it up too! I use the included USB-C cable to connect it directly to my MacBook. It's much more reliable that way, especially if you're on a flaky WiFi connection.