First, thanks for the excellent book! A lot of good stuff - the PS cmds for "harvesting" the WSPs from 2010 is worth the price alone, IMHO.
We have about 950 sites in 7 web apps in 2007, plus 2,600 MySites. We were planning to use db attach to move to 2010, and I set up a dev 2010 farm for that. It's gone pretty well in testing, a fairly high-fidelity migration path. However, we have had many, many delays on the infrastructure side that prevented us from migrating when planned.
So we've looked at our watch and it seems that as soon as we finish the migration, train users, etc, the next task would be to start the 2013 migration. We're evaluating now if we can do a second db attach move to 2013 before we give it back to the users. I've set up most of a 2013 dev farm and we're getting started. Our plan would be to do one web app over a weekend - the users leave 2007 on Friday and come back in to 2013 on Monday.
We are going to need CBA instead of Classic Authentication, for OWA if for nothing else. I have seen a couple of references to "convert to CBA in 2010 and then migrate to 2013." But then as your book says, CBA in 2010 was "rough around the edges". So, my question: should I convert in 2010 or in 2013? Looking at Migrate from classic mode to claims-based in 2013
I can't tell which would be better. Your thoughts would be greatly appreciated. Thanks again.