Font spacing is off in the editor which is a problem with Java 7: http://bugs.sun.com/view_bug.do?bug_id=8020752
It does not affect all font sizes, so try a few different ones until you find one that works. The default font, Menlo Plain 12, does not have this problem.
Update 2014-08-08: Java 1.7.0_60 solves this issue.