In Creative Suite 4, Dynamic Link was a one-way street. If you used Dynamic Link to send information from, say, After Effects to Adobe Premiere Pro, you couldn’t later use Dynamic Link to send information from Adobe Premiere Pro to After Effects. You had to restart the applications to reset the direction and use Dynamic Link going the other direction.In Creative Suite 5, that limitation is gone.
This is a huge improvement. But most people didn’t notice, because we didn’t trumpet this in our lists of new features. The only way that you would’ve known is if you noticed that the note in the CS4 documentation about the limitation had vanished from the CS5 documentation.
Read the rest, with links to more info and a reminder to use the free CS5 updates to avoid common bugs.