I haven't had crashes but whatever system loads the map doesn't always work. I plan on spending more time with that later to figure out what's going on. Other than that, loving it.
iOS 8.4 update on the iPhone 6 - 64meg - Multiple flights with ZERO issues. As always, I close all iPhone apps and perform a 'hard' power off. And after a clean 'power on' I only run the SOLO app and the requisite WiFi. Not sure if this procedure is entirely necessary but it seems like cheap insurance. Zero issues.
iPhone 6plus, only issue with app was gopro video on first flight, solved with methodically launching controller, solo, app last. No issue with update.