As the testing of the compatibility in an artificial testing environment might be helpful it wouldn't meet our goals. Therefore we(QE) started a community program that should give us more reliable results.
We received reports for 5 different products. You can look at full reports at http://wiki.netbeans.org/NB65BackwardCompatibilityTestingReport. I have to say that we expected more reports then "only" three. On the other hand, these reports are from people and companies that build real product on NetBeans Platform for years therefore we are happy that they haven't found any incompatibilities in NetBeans Platform - platform9 cluster of NetBeans IDE 6.5.
We will start similar compatibility testing for NetBeans IDE 7.0 when it will reach its Beta.
It seems that it repeats every release. The worst bugs appear a second before the end of the release cycle. I always think "did we forget to test this situation?". the answer is "No". We did our best. Unfortunately, we are not able to cover all the different configurations and usages that the users can create. As written in various 
We are testing accessibility this week. It means to check all the dialogs/menus/wizards/etc. in IDE that they implement Accessible interface, that the provide AccessibleName and Description. We also check the correct mnemonics, tab traversal. This kind of testing is required by Section 508 - 




