We have not officially released firmware 2.1.8 yet (still finishing up documentation). This firmware is primarily focused on OpenSprinkler 3.0 — the only part that’s relevant to OpenSprinkler Pi is increased maximum number of expanded zones and increased maximum number of programs. Unless if you need more than 56 zones, or more than 17 programs, there is no need to upgrade to 2.1.8 for OSPi users.
The app issue you were referring to is only relevant to OSPi. For OpenSprinkler 3.0, we recommend upgrading to firmware 2.1.8 if there is any WiFi connection issue. Otherwise, firmware 2.1.7 works just fine. The reason we are still finishing up documentation is that this is the first new firmware released after what comes with OpenSprinkler 3.0 (firmware 2.1.7) so we want to make sure the firmware upgrade instructions are clear to minimize the number of potential issues.
My reply here has details about specific changes in firmware 2.1.8: