I started the NB6.8 and had to wait for more than 15 minutes to get the autocomplete window (Alt+Space didn't show any results). That probably because it indexes the sources (I imported the JDK's shared classes into the project). The same task don't block Eclipse and IMO runs faster there.
Some of (my) students consider using eclipse instead because of this thing.
The eclipse seem don't bother indexing classes (at least that don't block execution and not so noticeable)
I don't quite understand what "importing JDK's shared classes into the project" means. You can browse JDK source from any project without importing it anywhere (they should be found automatically as part of project platform), thus no need to index them. Please provide more details about your project setup and size.
without answer for long time - closing.