very usefull when you want to keep an eye on your rig while away from it, you can even restart it, overclock, undervolt, check temps, and musch more while using the free edition. Honestly, i couldn't ask of anything more (except for a few things, but they are covered by the paid version)

Minerstat, especially with their OS helped me manage my rigs easier and remotely. The paid version with alarms, triggers and Telegram bot is worth the price! Come on, if you're mining it pays itself, since it saves you from errors and downtime.

Minerstat is really easy to use (configuring the actual miner can be complicated though). I switched from using the desktop version to the minerstat OS and it has worked flawlessly after properly configured. Any instability I had in windows is just gone as well, and getting more hashrate and efficiency out of my system now.