You misunderstood what my complaint about the poster images was: Powerpress CREATED poster images using the podpress default image, a URL that became invalid once podpress was removed from the site, and I believe that is what caused the editing problems.
Powerpress set the enclosure poster image to be the default podpress poster image, but that image ceased to exist when podpress was deleted from the site. I'm not 100% sure, but I believe that image becoming an invalid URL lis what caused the editing problem... and to me, that problem should not be ignored.
I was unable to save any edits on any posts with audio enclosures. The posts with video enclosures still had valid poster image URLs, and saving edits on those posts still worked fine.
For the posts with audio enclosures, only after I selected "modify podcast episode" and cleared that invalid poster image URL out of that field could I save my edits.
If it globally affects behaviors in WordPress, I don't think that's a "just ignore them" issue.
If I'd never gone back to edit some of those old posts, I never would have known the problem was there, or that it had been introduced by the Powerpress conversion.
What I don't know for sure is if that happens with all invalid image URLs, or if it's just a podpress conversion side effect, but it's something folks should be aware of.
My guess is that if I hadn't selected the options for Powerpress to use the podpress data it might not have done that, but since not doing that would have made the old podcast episodes non-existent, that wouldn't have been an optimal choice :)
So couldn't there also be an option for someone to choose whether or not to allow Powerpress import those poster images?
For anyone who's not been using them (despite the fact that podpress inserts the default in there for every enclosure), Powerpress could just acknowledge that option, drop that field, and any potential WordPress editing problems caused by having an invalid poster image URL goes away.
As for the find/replace tool, that is not an option with the current media host... the URL prefix is unique for each and every file, and as such cannot be updated that way.
Granted I would have had this current media problem with podpress too, but previously all I had to do was update the default media URL in podpress, and ALL posted media would automatically use that prefix... no search/replace needed.
I do like Powerpress because it isn't as bloated as podpress, but there are still some things that podpress seems to make simpler and do better, and for a lot of these shows & sites I'm maintaining, I first have to figure out if the extra work of cleaning up data after a conversion to Powerpress is worth it or not to me, each time it's time to do a site update.