1) Upgrades over time assume that the cables for future equipment
continue to be available. If this hub company goes out of business are
the connectors to the hub side generally available? If so, can you make
up your own cables instead to save money. If not, then I'd be really
worried about the future viability of this system if the connectors are
sole-source.

Good point. Just because I have somewhat of an upgrade plan now,
doesn't mean I will have the same plan 2-3 years from now. Lots of
things change in a couple of years, and I may change my mind on
components in the long term plan and end up with components
incompatible with the hub

2) Each connector in the wiring harness represents one more potential
failure node. The hub necessarily adds two connectors for each signal path.

I'm assuming you meant "un"necessarily adds two connectors, but that's
a good point too! Fewer potential points of failure always make
troubleshooting easier!

3) If you factor in the cost of the hub and the cables, you are close to
parity on the cost of an install using a custom harness

That's my biggest concern! $600 for the hub and ~$100 per cable, plus
the cost of wiring the hub in! It could end up being a wash...

You might ask one of the avionics retailers such as Eastern Avionics
what they think of such a system, since they sell lots of avionics that
they do not install. You might also compare the price of this system to
Eastern Avionics pre-fabricated wiring harnesses, which are sized to the
length you need for your panel.

I'll definitely ask around, before purchasing something like this... I
was just curious as to whether anyone had experience with it.

Thanks,
Todd