I just upgraded from 4.1.3 to 4.1.5 and now it takes ages to load my data model design. The progress bar sits at about the 40% mark for about 10 minutes.
(In case it's relevant: I had a problem where my domains did not get migrated, so I had to copy the defaultdomains.xml file across to the new installation manually. Unfortunately when I open the data model, all the domains have been removed from all the columns throughout my data model. It's going to take ages to put them all back on again )
I tried it in 4.1.3 again and that's slow too, so something in the upgrade has done something to the data model files.
Unfortunately this has ruined SQL Developer's data modeler for me, as I've just started build on a new large application and was using data modeler extensively. That'll teach me to take regular backups of everything