GUIDs in RSS rock
Guids sure have a funny name, but they're quite useful. If your weblog tool supports them, use them. If not, ask the developer to add the support. It's not very hard.
Further, I strongly believe that all aggregators and readers should pay attention to guids where they are available. It's a convenience that many users will appreciate, especially people who are in a hurry
Haven't really been saying much lately about the recent plunge, albeit more amiable this time, back into the RSS and weblog syndication frey. Mostly because I haven't had the time, and mostly because people more eloquent than I were already saying what I thought.
In the meantime, I've been working, and puttering around with my own aggregator as spare time comes up. And you know, I'm tired of having to come up with some mechanism to detect new entries. This GUID thing is what I need. I don't want to run MD5 on another RSS item, and I don't care to track the minor edits people do on their entries, like Dave said.
Personally, I think the GUID should be the permalink, if at all possible. I used to think that that was what the link of an RSS item should be, but then I never really maintained a weblog in the quote-link-comment style for long stretches. My entries aren't usually completely about someone else's article. But, some weblogs are like that. So, link points to a subject under comment, GUID identifies the entry and ideally does it via permalink.