The startup time for NetBeans 6.5 Beta has improved a lot. After deactivating not so frequently used plugins, the cold startup time is just 8 seconds which is amazing compared to the performance of earlier versions of NetBeans [I am not working for Sun or related projects :)]. My laptop configuration is Intel Core 2 CPU @ 1.66 GHz and 2 GB RAM with Windows XP.

To speed up NetBeans [deactivate plugins] go to Tools--> Plugins and deactivate unused plugins one by one. [Choose the option to restart IDE later if you have more plugins to deactivate].