Native PLSQL execution has changed significantly since the version 10G. The effects are less than spectacular, in the ideal case I got about 10% of the performance boost. This is much easier to administer now, there are no shared libraries in the file system, as was the case with version 10G. Oracle has re-invented the dlopen routine, with the shared library residing in the database. The gory details can be found at:
On the same web site, there is also a PDF version of the same page but WordPress displays some inane commercial, rather than to point to the PDF, so the PDF link was replaced by a HTML one. PDF, however, looks better, at least in my opinion.