As with many things, I guess its utility depends on your use case. If you need access to the Pi i/o pins, and need to be away from a power outlet at the same time, I suppose something like this is necessary.
For a portable Pi without use of i/o pins, I have a couple options. If I'm in a hotel, say, I can just plug the Pi into the TV along with a keyboard and mouse. If I have to be away from a power outlet, and/or away from something I could use as a monitor, using an old laptop with RPD x86 on it gives me a Pi-like desktop environment in which to work (I recognize that such is not truly a Pi).