One of the frustrations of updating to a new version of NetBeans (e.g. from 6M10 to 6B1) is having to recreate all my libraries again. On projects that use a lot of libraries this can be very time consuming.
The solution to having to recreate all the libraries when upgrading to a new version of NB however is detailed here. Basically, each library is described by an XML file which you can copy from one installation directory to another. Simple !