One thing I noticed is that the Formula field still goes directly through a eval().
This has some not-so-intended consequences that can be used as features, but they do cause some bugs in some specific situations.
One such bug is that characters set to Auto-Battle go through their entire skill list at the beginning of each turn, and they do run the eval() in each skill. Normally, this would only return a number (the result of the damage formula). But if you type a command in the formula field.... this command actually gets executed at the beginning of every turn.
So, if you have a formula that begins with:
a.gainMp(20);You may notice that characters set to Auto-Battle (who have access to this skill) will gain 20 MP at the beginning of every turn, even if they never actually use this skills.
This doesn't seem to affected Confused characters, nor Enemies. So it appears to be safe to use as long as you don't use Auto-Battle.