I had the same issue others are reporting where you just have the base map after the upgrade, despite downloading 2 Gigs of detailed maps. I deleted the app and re-installed and then redownloaded the maps, and all is well again. If you use iCloud to sync your favorites they should still be there. Garmin needs to fix this, but until then there is a workaround.
LimeyGarp about Garmin N. America