Hi Deleted. Glad the progress you're seeing is giving you the confidence to move and/or advise your customer on both modern experiences and SharePoint in Office 365 all up.
A few quick comments on your comments:
1. RE:Search - we published a new blog on blogs.office.com that highlights what we're doing with Microsoft Search launched #MSIgnite:
https://aka.ms/SharePoint-Ignite-Search ; we do have extensibility plans on the roadmap as well. (Cc: Naomi Moneypenny)
2. Settings - we're working as hard as we can to up-level all important settings to the new, modern edit panes you see inline.
3. Understood, and for some apps where SharePoint was the focus, we now have new services like Planner, Office 365 Groups, etc).
4. We do suggest people move away from subsites, though support them going forward if they exist, and if created now going forward, they would have a modern look, too. More guidance in the SharePoint hub sites planning guide: https://aka.ms/PlanningSPhubsites, and the new "Build your modern intranet with SharePoint in Office 365 resource center page: https://aka.ms/SharePoint-build-modern-intranet.
5. Page layouts: we're working on page designs (like templates) to address these common scenarios.
6. Nav support will start with mega-menu, and then move to additional scenarios to further control how and if it appears.
7. Bugs will always crop up, and we'll keep exterminating 'em. Let us know when you see one.
Cheers,
Mark