I don't have one, and have not done any actual hardware work with one, but i have helped people do the software setup on several EFIS panels who used the Hub system for their wiring. I can say that the documentation is very thorough - to the point of giving the owner so many charts and tables that I spend more time trying to figure out what channels are talking to what than I do actually setting things up. If an owner had done their own wiring, they could probably tell me with a very simple set of chicken-scratching what wires go where.
I don't want to say anything bad about a product that I really haven't used, and from what I can tell, the Approach System folks are really trying to provide a solid, accurate system for people. I have heard people say before that if your system is very complex, it is better to wire it with a custom harness, and if it is simple, the hub might be OK. In my view, the first part of that is right on - if you have a very complex system, it will probably be easier to figure it out later if you have done the wiring, or if you have a custom harness built. And if your system is simple, then it is actually pretty simple to just do the wiring.
However, I acknowledge that it is very easy for me to dismiss it since I have been fortunate enough to have enough experience to do my own wiring. A lot of people see the panel as a bag full of snakes that make no sense. If that's the case, and you're planning on paying to have your wiring done, I'd suggest talking to someone like Stein, and see what kind of advice he'd give on going custom wired or Hub. In my limited experience, you are as likely to have to learn something about your electronics with the Hub as you are with a custom harness - or if you build it up yourself. And learning about how it all works is a GOOD thing!
(This is a little bit of a Mac vs. PC thing....)