A few of us have upgraded and tested the latest release of the Autopilot firmware. Follow these steps to manually upgrade your firmware on the Solo from a computer running Windows with WiFi:
1. Download the firmware,
ArduCopter-v2.px4. Use firmware tagged 'Latest release'.
2. Download and install
FileZilla or
WinSCP.
3. Turn on Solo and Controller.
4. Connect to Solo's WiFi network from your computer (similar to how you would connect your phone to it via the app).
5. Launch FileZilla or WinSCP and connect to Solo using it's IP address '10.1.1.10' for the Host and 'root' for the Username and 'TjSDBkAu' for the Password. Use port 22.
6. Copy/transfer the firmware to /firmware on Solo.
7. Reboot Solo.
8. After reboot the LED's on Solo should change colors (party mode).
9. Accomplish a Level Calibration.
Enjoy!