Hi Nick,
My team has been working in the authoring tool for about six months now. We have 6 training writers with varying technical skills working in the tools and aside from some initial struggles with the 0.1.1 version, we've had no significant issues with the latest release. It takes a little bit of time playing around to figure out what all the fields and buttons do, but after you get the hang of it, the authoring tool is in the tool is dead simple even for non-technical users.
We do use the single user account. While it doesn't quite feel "right", it hasn't been a roadblock for our team so far. The only issue is that there are some other groups within the organization that have seen what the tool can do and want to use it too. We don't quite know how to support them and deal with permissions, change management, etc without full user management, so we've had to turn them away. :(
We receive daily compliments about how beautiful/stunning/gorgeous/etc the courses look. We did put a lot of effort into customizing our theme and the graphics templates we use, but if you have one or two developers who can take care of that for the non-technical users then you're good to go. As Paul mentioned, creating your own plug-ins or adding schemas to existing framework-only plug-ins is not overly complicated if you have some coding skills on your team. And if you can contribute any of those changes back to the community or to the plug-in owners, then even better!
There is currently no easy way to import/export courses from the authoring tool, but I know this feature is high on the list for the core development team: https://community.adaptlearning.org/mod/forum/discuss.php?d=988#p4780.
Otherwise, my advice would be to make you sure have a solid backup strategy, use a different server to do your theme/plug-in development so you don't take down the production server, and don't be afraid to use the forums, they've been incredibly helpful and responsive. :)
Good luck!
Ryan