Looks like the long overdue PS5 is released. The main change is from Contribution Folders to Framework Folders. Oddly enough both are still supported even though Contribution Folders are obsolete. And of course you shouldn't confuse the two with Records Folders, although the new functionality blurs the lines even further.
The main reason for the change is scalability. Contribution
Folders were limited in size and were slow and unwieldy to use. Framework Folders have "no practical limits" on the number of folders or content items they contain. I guess now you can finally structure your unstructured content! ;p
Framework Folders introduce a "personal" folder where only you can view the contents. They also reintroduce "query" folders, so that any items can be exposed to webdav via a search. (Contribution Folders have similar functionality but 10g disabled it by default.) There is also a "retention query" folder for searching for records via webdav. Framework Folders also have a new feature where the user can switch between viewing only released content or viewing all content (includes stuff in workflow.)
Another welcome change is the uh, dumping of the Trash bin. Items can be either removed from folders or "deleted" - which just marks them as expired. It is a much more sensible solution than the confusing Trash bin or destroying content.
PS5 provides a migration tool for switching from Contribution to Framework Folders (you can't use both!) and if you are using WebCenter Portal, Folders_g must be used and not FrameworkFolders. There is no tool for migrating Framework Folders between environments though, hopefully Archiver is up to the task.
Oh there's no improvements to the dud OracleTextSearch.
UPDATE: Forgot to mention that Framework Folders allows you to search for folders. Actually Contribution Folders already had this feature but it is not exposed... the form is broken anyway.