I'm not really expecting anyone to go back and tag things for me, but who knows, they might. I also think that I'll start using tags more. Maybe even write some scripts to set tags based on old content in entries: things with "ipod" getting an ipod tag and so on.
For the record, for the S2 users among us, the key for tag editing is "edit_tags". I'm sure this is documented somewhere, but I only found it by looking at LJ/S2.pm in the code. I wonder if there's some magical S2 documentation that I don't know about.