Can't speak for FireBeyond or dorian-graph but I too am running it on my regular, everyday iPhone 5 and have found it surprisingly stable.
Any actual crashes seem to be a result of doing too many things at once, particularly during an animation (eg: close out of an app and double-click for multitasking before the animation is finished). The crashes seem to cause a restart of the Springbord app rather than a complete system reboot, so it comes back within 10 seconds and hasn't lost any data (it even keeps the same song playing in the background).
Any actual crashes seem to be a result of doing too many things at once, particularly during an animation (eg: close out of an app and double-click for multitasking before the animation is finished). The crashes seem to cause a restart of the Springbord app rather than a complete system reboot, so it comes back within 10 seconds and hasn't lost any data (it even keeps the same song playing in the background).