"integration" ?? Do you mean using jbuilder with 1.3.3 and adding 1.4 to the list of target jdk or running jbuilder itself with 1.4?

Neither is supported by borland. The official "non-official answer" is that you should wait until the next release. Several reasons for that:

• there are some pretty nasty bugs involving running 1.3.1 to debug a 1.4 VM, as well as some incompatibilities between the jpda implementations. One guy at borland was saying officially 'non-officially' that they are nasty enough to warrant waiting until Sun fixe them.
  
• running jbuilder 6 over 1.4 also has its share of problems. In particular, the new focus manager architecture will force borland to recode all the wizards.
  

All is not that grin, though. I have been using jb6 over 1.4 since january for server side development. Except for the odd (read annoying) problem with some of the dialog boxes, I am totally satisfied. The speed and L&F improvements are well worth the minor troubles.

hope that helps
laurent