Makes grip much more reliable and comfortable, probably will increase chance of survival if you drop the Orba. But more valuable is that it reduces chances for that drop to happen. "Bump" action note still plays good.
Only downside is that Orba wearing a silicon sleeve does not fit Travel Case anymore. Like, completely. You will have to choose one or another for the constant usage, removing the sleeve to put it into the travel case and dressing it up again before playing - will be too much of a burden, considering that this Orba's strongest side is being useful for starting playing spontaneously.
I am not sure if having them both really makes any sense. I have both, and use the silicon sleeve all the time, while travel case lives somewhere in the drawer, empty.