The issue I ran into with my 1520 this morning (and I've got that 128GB Sandisk in there...) was the upgrade seemed to go smoothly but any App that was accessing the SD-Card (Camera App, Photo App, Video App, Storage Sense App, etc... etc...) wouldn't launch at all when invoked. A simple power-down and power up wouldn't fix the problem, and the soft-reset resulted in the BSOD. After that I pulled the SD-Card, did a power-up-hard-reset and other than having a wiped phone, all seems to be well.
That the problem is related to the SD-Card is pure speculation on my part but historically this is not the first time that the combination of the two (MS Dev/Test O/S plus SD Card) has caused me grief as I had similar issues with the upgrade from 7.0 to 7.5 on a Samsung Focus and then again with an early version of Nokia Amber on a Lumia 822.
You'd think I would learn....
I'm up and running though, just plugged the card back in and have copied my Music library over. One thing I like about the new Music app is that you can now tell it to look at "just" the Music on the SD Card, xBox Music Cloud, or Both. Much happier about that. Album Art recognition seems to be better as well but it still missed a few when moving my music over.