I don't think this has been posted anywhere, which makes me think that it's new info.
There's a reasonably lengthy Stealth excerpt in the rules compendium on the wizards site.
http://www.wizards.com/default.asp?x=dnd/insider/compendium
I can't link directly to the article, but just search for Stealth from there.
The changes seem fairly small, but do look like they get rid of some of the bizarre stuff people were trying to do with stealth actions.
It is a better written rule, but it is a huge nerf.
But it is likely to go away.
Baring a new announcement, the Compendium does NOT yet over rule the PHB.
When it first came out, myself and others found a few discrepancies between the PHB and the Compendium. I emailed the ones to Ken Troop (think that's the right guy for DDI) and got an email back that yes these were errors and thanks for reporting them.
Having seen all the differences between the PHB and the Compendium, I have to guess that the data they pulled for the Compendium was from an older version of the PHB.
I will say this: the stealth rule currently in the Compendium is a lot clearer.
But it is also more limited to the point of being superfluous (why bother stealthing if I'm already in total cover?) and quite back to the old 3.5 iteration of stealth and contrary to what developers have said they've intended.
The DDI news article for the Compendium calls it a 'first glimpse.' Have there been any other announcements? Since that time, communication from DDI staff was that they knew there were errors that they needed to fix. Since this is so contrary to the PHB, and no faq or errata agrees with it, I have to count this as another error and not a new rule.
One more confirmation that it is not official: this entry is not used by CS in their responses to our questions. They may or may not be consistent on their interpretations but they do go by the official sources. If the Compendium was official, it would be an invaluable tool to CS in their job.
If anyone has word otherwise, please speak up. This is not a new rule on stealth.