What I've noticed so far...
The "Nav" icon in the upper right corner (while in radio mode) is different. I haven't seen much difference in the actual Navigation software though. When I go into the Navigation, the first screen looks pretty similar to what it looked like before the upgrade. I did notice that there were 3 Garmin 'sites' listed in Favorites that I don't remember being there before. Those were deleted immediately. I don't use the Nav a lot, even here in the Twin Cities, so there may be a lot of changes that I just haven't noticed.
I don't use the radio (AM/FM/Satellite) so I can't tell if anything has changed/improved there. I use the HDD and AUX features. I noticed that after the update the AUX button is greyed out unless you have a device plugged in OR have your smart phone running a media app (for Bluetooth streaming). I have noticed that the HDD seems to react faster, especially at initial start-up. There have been times where it took over a minute to show the current song playing, now it's usually showing the song by the time the "warning" message goes away (I stopped pressing accept after the first week or so since it starts playing music while displaying the message).
If anyone reading this owns a 2012 with the 430/430N and for some reason doesn't get the update CD, let me know. I'm sure I can work out a way to get an ISO image of the CD and scanned images of the 'booklet' to you. I have a Google Drive account so if you have Gmail I can give you temp access to a folder and upload the ISO/scans there for download.
Burning an ISO is pretty easy, you just need a CD burner and software like this (my favorite DVD/CD burning app):