I've been running Ubuntu 7.10 on europa, with basic 3D hardware acceleration via the native ATI drivers and some of the eye candy turned on. I have been pleased with just about everything except where noted.
I decided to install the latest NetBeans 6 release, RC1. I downloaded it and installed it, and then fired 'er up. The first thing I noticed was the performance. It is, in a word, abysmal. It starts up slow and it runs slow. And I do mean slow. Up to this point developer releases of NetBeans 6 have not had such drastic performance slowdowns. And this performance slowdown is only observable on Ubuntu 7.10. NetBeans 6RC1 runs just fine on Windows XP SP2.
The problem presented an interesting opportunity to compare NetBeans 6 RC1 with the version available on Ubuntu via Synaptic, NetBeans 5.5.1. Using Synaptic I found and installed that (current) version of NetBeans and started it up. The screen shot shows both running on the desktop. Version 6 RC1 is on top and version 5.5.1 is running in the back. In order to level the playing field I added a configuration switch to netbeans.conf: --laf javax.swing.plaf.metal.MetalLookAndFeel
With both IDEs using the Metal Look-and-Feel, NetBeans 5.5.1 ran rings around NetBeans 6RC1. I have no idea why. In the mean time I'm going to use the NetBeans IDE provided by Ubuntu, along with the Ubuntu provided version of Java, Java 6 Update 3. Talk about a nice combination.
One other observation. The latest version of Eclipse, 184.108.40.206, has no performance issues either, and that version I downloaded and installed from the Eclipse site.
Update Nov 21 2007
Please see my update post about how RC1's performance was corrected.