Are you asking about Marketing users that will use Marketo or Sales users that will use Sales Insight?
For Sales Reps, the Sales Insight training is done in-house for about 1 hours, but I also provide them links to several Marketo Sales Insight resources including a 5 minute video intro.
For Marketing users, H. Other, Tell me more. We have new users that will be using most of Marketo attend the Foundation Build Workshop. I provide all new users in-house training (after the Foundation Build Workshop if taken) that can last a few hours to an entire day depending on the scope of their role. My ongoing training is based on the latest info in the Community and Marketo University. I use that as the basis for on-going training of other users and/or I direct them to those resources when appropriate.