I\'ve been coding basic UIs in Java manually and using NetBeans, but recently switched to Eclipse Indigo. I use the visual class builder to design SWT user interfaces in Ecl
You can also use Jigloo.
Their eclipse update site it, http://cloudgarden.com/update-site
I have used it in windows quite well. But when I use it in mac, most of the time it crash.
But windows builder seems better to me.