Don't know if it's device specific (or sd card related), but News is slow/laggy and Groove really isn't any better than the old zune app performance wise. Signing in alone takes too long. Outlook is fantastic tho, won't argue with that one.
So, I'd like to know what apps you guys are using that are appreciably better. I don't notice an improvement in load times and responsiveness compared to the better wp8.1 apps. And definitely nothing that compares to the "instant" and rock solid feeling of top tier android/iOS apps.
Maps on W10 is a lot better than HERE on 8.1. Not performance related, but features(lane suggestions, left/right side of street of destination info, traffic cams, etc). Performance for Maps has been great foe me though. Just missing the transit HERE app, though I only ever used that in France. The public transit in Atlanta is about as simple as you can get, and almost as useless.
Performance on apps such as News and Weather depends on network performance as much as anything else since it has to go grab crap to display. I am in the app and waiting on content to be fetched within 2 seconds for both of those.