Yes you should migrate to CGLib 3.1 because it can correctly generate stack map frame and deal with Java 7 bytecode.
Update
The following issues were all addressed by CGLib 3.1
We're using EasyMock and switched to a custom version of CGLIB 3. We switched because code coverage with EclEmma/JaCoCo/Sonar would no longer work. It was more or less a drop in replacement (apart from updating POMs). Unfortunately
CGLIB 3 is not (yet) in Maven CentralCGLIB 3 has a blocker bug https://sourceforge.net/tracker/?func=detail&aid=3601081&group_id=56933&atid=482368 so we had to build a custom version and deployed it to our in-house Nexus
So if you don't currently have any issues like code coverage no longer working I would not switch.