Was sweating bullets over this one - so thought I would post this here in case anyone else is worried about upgrading.
I just went from 3.3.1 to 4.8c and not a single hiccup as far as I can see. Whole process took less than 5 mins - including d/l latest version from here and re-uploading.
I deleted close to 100,000 images first just to make it easier for the script - but in hindsite probably didnt need to.
Thanks photopost !