selectively cascading portlets
In versions 2 and 2.5 of Plone the portlets were created as pages and you could just point to them from the relevant folder level and so have one portlet selectively cascading at different levels of the site. This system was a little complicated to use but it did give good flexibility and avoided having to create the same portlet multiple times at different levels. In version 3 it seems to be all or nothing - I can block or unblock the portlets above in the folder structure but I can’t say ‘do block this one but don’t block this one’.
Adminjonstahl (Admin, Plone) commented
You can do "global" portlet ordering with collective.weightedportlets (http://plone.org/products/collective.weightedportlets)
There is missing also a "global" order for portlets if you don't want them to be ordered by folder hierarchy. (see Solgema.PortletsManager)
AdminEric Steele (Admin, Plone) commented
In addition to what optilude said, Plone 4 introduces a show/hide button for each, allowing you to hide individual portlets anywhere within the site.
Adminoptilude (Admin, Plone) commented
I'm pretty sure the portlets system in Plone 3 supports everything that you could do in 2.5. Portlets inherit in much the same way, and you can explicitly block and add new portlets at any level. You can also re-use old portlet page templates via the 'Classic portlet' type.