I'm against all the "notify me when a post I downvoted is updated" requests, but I had an idea that might be useful while unobtrusive.
How about quietly showing how many revisions/edits were made between your downvote and now? It could also "clear" when you recheck the post, so they don't stay marked as "updated"
The % edited and revision count are just ideas to help show the magnitude of the change. If someone changes "Im" to "I'm" the revised post probably isn't even worth a look, so I think the % edited is a good criteria to go on. I could at a glance (and on my own time) see which of the posts I downvoted/close voted have been updated. Maybe make the (% edited) text a link to the latest revision so I can see what changed (I often do this when I forget why I closed a question. It happens.)
As a mod it'd be really nice to see when posts I've closed have been edited as well; ideally users would flag/vote to reopen a post when it's fixed, but very few people seem to flag.
This would make it easy for us to optionally review our downvotes/other votes without making voting a massive burden (some proposals requiring comments/notifications on posts we downvote could easily get very invasive and annoying).