I have a Stratus 3i, and while I've had a few issues, it works fine for me.
The issues.
1 You'll need an iDevice capable of loading and updating the latest Stratus Horizon Pro App (Free at the App Store). They don't (yet) have an android version. The app will let you flip the "Open ADSB" switch that allows the iFly program to communicate with the Stratus 3i. It also allows you to reset the Stratus 3i to Straight and Level, if it gets out of calibration.
2. If someone uses ForeFlight on your Stratus 3i, the ForeFlight will switch the Open ADSB switch to the Off position. You'll need to turn that back on if you want to use iFly. ForeFlight and iFly can NOT be used with the Stratus 3i at the same time.
3. When I loaded the last firmware update for the Stratus 3i, it changed some settings that I needed to find and reselect before it performed as I liked. I've only done one firmware update, perhaps there won't be any more, or possibly they'll not have the firmware change user settings.
I too built a StratuX and liked it, except for having to set it up each time I flew, and agree that, for the price, it can't be beat. The StratuS 3i came with the ADS-B transponder we had installed to comply with the 2020 ADS-B mandate. The Stratus 3i is mounted out of sight under the dash, so less clutter.