Thanks. I actually came up with similar techniques to these (blur between edges, shift and feather image behind and erase top scratch) but my implementation didn't work as well as the ones you described, and i ended up getting best results until now with clone stamp. I guess it'll have to be more or less as it has been for the previous photos but i can definitely see some cases where the blur will be very useful.
The time is mostly in selecting all the scratched area--it is irregular and i can't get it with the magic wand. Are there some tricks for selecting narrow, jagged areas more easily? Typically i also need to include a few pixels on either side because it is the bunched up print. I don't know how to select something like that.
I did a lot of searching on this and actually didn't find much in the way of tools for any app. It surprises me with how common the task must be but it seems it's a pretty tough thing to automate.
I'll let you know if i come up with any refinements on the technique.