I just stumbled across a 2010 limitation that I have not seen before. When creating task custom field formulas, PS will give you a nice red warning to have less than 5 task formulas due to potential performance issues. I believe that this is only a very general guideline, but certainly enough to have Microsoft warn you.
I will struggle at times to obey to this rule since I often use calculations within task custom fields, so EPM’es be aware and let me know if you have come across performance issues when using more than 5 task custom field formulas.
