You should follow these tutorials sequentially; they build on top of each other. They are now correct for 6.0, at least, for Milestone 10. They will of course be tried out again several times by the time the final release of 6.0 comes out. At that time, they will be linked to from the http://platform.netbeans.org/tutorials page.
A few small but annoying bugs in the series have been fixed, mainly thanks to Roxie Rochat. Thanks Roxie! I found some of your e-mails where you reported several issues that had not been resolved, mainly in the third part of the series. They're all fixed now, though I need to check your e-mails again several times to make sure. Something Bennie Vaessen reported has also been fixed.
However, a few small things must still be worked on (e.g., how to correctly replace the usage of ErrorManager) and the final solution of the 4 tutorials (as well as individual parts) will be made available to the Plugin Portal, and then referenced at the top of the tutorials, by the time 6.0 comes out. (Update: The completed sample can already be downloaded from the Plugin Portal. Click here to jump to the correct page, where you can simply click the Download button.)
Purely as an exercise or refresher, I highly recommend that every NetBeans Platform developer should go through all 4 parts of this series at least once a month. Irrespective of your level of skill and knowledge. I'm willing to bet that you'll learn something new each time. From Lookup to Nodes to Property Editors, this series is really extremely broad in its coverage and helpful in its explanations. Big bonus in the 6.0 version—I added lots of new screenshots, to soothe the weary eye and sustain you on your journey!
In other news. A concise and persuasive testimonial about the NetBeans Mobility Pack, by someone who is actually using it:
Why I use NetBeans Mobility Pack to write Cotopia.