I noticed slowness in:
- startup when you launch the application
- the user interface when clicking from one notebook to another (I See "loading notebook..." a lot in V10, not in V6.25)
- clicking on a link and seeing the note details. It looks like V10 needs to get everything from the cloud, while V6.25 has everything local)
- syncing when I enter something in Windows, and when it is synced to the cloud.
I have 19.000 notes synchronized in my notebooks and use a 200 mbit symmetrical fiber internet connection