I just updated my ST to the latest v4.6. Other that 'BlueTooth Audio' sounding better not 'Bluetuth', the biggest added option is to 'ReBoot Sync'. At v4.3, one point Sync wasn't working at all, no BT, no USB, but I just pulled the fuse which fixed that. I've upgraded to all 3 versions.
Months later I also got a 'Index Full' which was the reason why i wanted to do the update to v4.6. But first time trying the update failed halfway; it would up doing a master reset before it failed. After re-pairing it stopped 'Index Full'; anyways a week later I figured I'd do the update anyways, so far no problem or issues. I'm not totally sure why it failed the first time; second time i used a 2GB Flash (not a used 8GB stick), Fresh format FAT32, Extracted the Zip file straight to the flash drive. Worked fine second time.