PO can easily become a big problem if u ignore tax settings and start upgrading stuff to level 3-4 without a plan, combined with heavy military research and/or lack of clear provinces assigned for food, army or money production.
If u keep everything level 2 initially, add grove/farm minor and theater/delicatessen/grove in capitol it's simply impossible to have unrest from squalor.
Capture some world wonders and add some PO from philosophy and your able to start upgrading to level 3 buildings without much thought.
OP, take a look at this awesome guide;
http://www.twcenter.net/forums/showt...-Strategy-Tips