Getting NetBeans and Eclipse to work together isn't all that hard. I'm now cycling through the Sakai SOPI App re-work ( spec drift ) using both IDEs against the same checkout. One just has to keep the specific project dependencies wired up correctly.
I think I've figured out the NetBeans performance issues. Watching the OS X Activity Monitor I see that Eclipse uses all the CPUs in this quad g5. NetBeans will spike one CPU and grind away.
It's still dangerous to get ahead of NetBeans rendering!