My firm was fortunately committed to hitting the ground running, and invested appropriately.
Two days of reseller training. (Hi Ransom) Months of working in house with a consultant. (Hi Matthew. Maybe you can remember how many months.) I took DNC's 2-day GDL seminar, which along with the cookbook got me to critical mass in no time.
How did we have a consultant for months? Simple, he worked on projects, and we billed clients for his work. So we had an ongoing learning experience that was also productive. We never lost money on an AC project, not even the very first one.
AC was our first CAD system so we didn't have to battle a lot of ACAD greybeard eye-rolling. Fortunate there too.
My general thoughts on training and learning:
The virtual building approach is radically different from whatever 2D method you used before. To be successful, you have to attack. Accept that the transition will take time and resources and commit to investing them. You probably will lose money on the first project, but if you are committed you will make money on the next one. If you half-commit, you will be constantly backsliding, and getting told-you-so's from flatlanders.
If you're not committed to modeling, you're not really using AC and you can't master it, and experts can't really help you because you're not doing the same thing.
AC is too complicated to learn on your own, IMO. The documentation and the interface don't naturally lead you to mastery. Third-party AC for dummies type books are rare. You have to make personal contact with someone who is proficient, so you know what is possible. Then practice and ACTalk will get you to a high level.
Good question, thanks for asking.