I've installed the 4.2EA version of SQL Developer, and I've noticed that is somewhat slower executing Inserts and running some scripts. Nevertheless, there's a HUGE difference in the speed of the export functionality.
Steps to reproduce
1. In a SQL Worksheet, execute a query that returns at least a couple of hundred records
2. In the output, right click => Export
3. Export is very slow, taking a couple of seconds to export each record. I've tested export as Insert and also as Excel.
4. If I do the same in a previous version of SQL Developer (eg. 4.1.3), it takes just a couple of seconds to export ALL the records
EDIT: I'm running SQL Developer in Windows10 / 64bit / Java(TM) Platform 1.8.0_101
Hope you can fix this before release.