In my brief experience using it, it seems to work well for what it offers. While I had some issues connecting to the monitor console initially, that seems to have resolved itself.
However, I’ve seen apps from other companies with much better functionality. Our church moved from Yahama CL series consoles, and Yamaha’s MonitorMix app is a lot quicker to operate. It mainly comes down to being able to create grouping templates, where channels can be grouped and color-coded. This makes finding the channel you need to adjust way faster than with Venue On-Stage, which has no groups and no color coding, requiring you to swipe through every channel looking for what you need, and having little visual indication to assist you.
It does have a leg up over Yamaha’s app in that it features live metering on each channel, making it easy to identify channels that are clipping for example.
If Avid were to make those changes to allow for grouping and color coding, that alone would make the app a 5/5 so long as stability remains intact.