permalink change and Google status?

For those of you who have done a permalink change (with 301 redirect from the old to new URL) on pages that have strong Google position, was there any negative impact on the Google position of that page?

The reason I ask is something I found on this thread” over on the Google Webmasters forum. It describes a scenario in which, for a time, there would be duplicate content in Google, which apparently negatively impacts Google position.

This would occur when the new page has been found by Google via new site navigation and indexed, but before the old URL has been updated and the 301 noted by Google.

It makes sense, but I’d never heard that before. I would like to change all my permalinks, but it does take Google a long time to update _all_of my pages.

Thank you! -mm