I was one of the first dealers on the continent to stock the Alfine when it first hit the market. I had already sold and installed a couple when Sheldon was still posting about their anticipation of the arrival of the first units.
I also sold some of the first OEM bikes equipped with them (Brodie Ocho).
I remember having the conversation with the Shimano rep about why they were not shipped as complete kits. The explanation was that small parts kits were customized with anti rotation washers specific to the application, and a choice of cog size.
When the aftermarket buyers started realizing they did not have everything they needed to do the installation, the demand for those kits went through the roof, and I ordered as many as I could get, and sold them as fast as I could get them, mailing lots of them right across the country, even to bike shops.
As for functional issues, I never saw any that could not be corrected by ensuring smooth cable run and proper adjustment.
I sold one line of bikes that was particularly problematic in this regard with the Nexus 8. Re routing the cable housing to eliminate a tight bend from the cassette joint solved all those problems.
The only bike I can think of that actually had to have the wheel sent to Shimano to resolve was one I sold over the phone and shipped to Vancouver. The buyer had a local shop do the assembly, and they botched it. I don't even remember how they did that now, but I remember it was bad.