The microdata is much more data.
You can see this metadata when you post to Twitter or Facebook and it shows a preview.
We have the internal stats to show that this is MUCH more reliable than RSS but I don't really have it in a format that I can readily share.
Discovering the links can be done by just spidering every post on the front page.
The biggest challenge is the timestamp. We handle that by just keeping a fingerprint of all the URLs and we only index URLs that have either never been seen before or have timestamps.
I honestly with timestamps were required by Facebook and Twitter or at least given special treatment.
The special treatment strategy by Google and others has REALLY done a great job at upgrading the quality of the Internet by not breaking it.
Basically saying that your site will get some tangible financial benefit if you run X spec.
So if you enable IPv6 or HTTPS you get an SEO boost.
Companies actually pay attention to this and implement these changes.