Lesson one: break your news feed.
Here is a good example of what not to do when changing the backend that produces your news feed, illustrated with OsOpinion. Here is how I was greeted today in my aggregator:
Mmm'kay, so since they don't provide the new feed URL in the text, let's visit the link as advised...
Ah! Very helpful. So I had to visit the site, to find that the feed was moved from
It's not the first time I see this, so here is just one advice you may consider to avoid losing those of your readers who will not care following your moving feeds: Cool URIs don't change! Changing the URL of a news feed is strictly equivalent to changing the URL of your home page, since the feed URL is actually the site entry point for its subscribers. Would you break your home page like this just because you've changed your content management system? No one in their sane mind would accept that a CMS breaks a home page like this, so why accept it for a news feed? OsOpinion could have changed their backend without changing the feed URL.