In my spare time I've been reading about other factory turnkey electric bicycles. So far besides a Stealth none of them look very interesting. Even totally discounting price, I can see why home builders don't like the factory bikes. Almost every one of them traps you into using their purpose built battery, controller, motor, or probably all three. That means you better like their range, or power, because it's going to be difficult to customize them to suit your personal likes.
In comparison Stealth's are more like a home build, except made by a factory, or a very above average home builder. There's nothing special about most of the individual components, and that's a big advantage Stealth's have over the competition. It's only the combined assembly that makes a Stealth different from your home built bike.