One sort of unrelated thing is an issue I found when I started to migrate code from 1.5 to 1.6. I thought I had all of my project related code changed over only to have a build script fail. Below is the stack from my console.
The error manifest it self in two ways. the first way is:
class file has wrong version 50.0, should be 49.0
The second way is:
[echo] compile of C:\_brent\workspaces\.....\source\main to C:\_brent\workspaces\.....\webapp\WEB-INF\classes
[javac] Compiling 144 source files to C:\_brent\workspaces\.....\webapp\WEB-INF\classes
[javac] javac: invalid target release: 1.6
[javac] Usage: javac