MS Dynamics NAV team has published recommendations for how to setup SQL for NAV. This is a great initiative since there has been a lack of this kind of documentation for a long time.
Here's some comments on the content:
I also read the recommendation to leave auto create/maintain stats enabled. We also prefer to turn auto create/maintain stats of on solutions with huge loads.
It would be nice to see some autoritative testing on this!
As a sidenote I have experienced that it is necessary to update statistics more than once a night when processing huge invoicing batchjobs otherwise performance turned out to be very poor.
But those stat updates are executed in under 5 minutes when the update statistics job is run.
I think that the cost for having auto create/maintain stats on would be way more than those 5 minutes needed to run the statistics update - but again it would be nice to see some testing on this.
But then again the need for statistics updates depends on the amount of data processed and the number of tables/indexes used and how they interact which makes measuring this fairly complex.
That Index defragmentation scipt is nothing new. It's been around for years.