In order for evasion class ability to work, you have to be wearing light or no armor. So, if you are dipping into rogue from a mainly cleric or fighter type build, then you will either need to wear light armor, or forego use of evasion.
For all the skilled players out there, how useful is evasion later in the game and would you take a -5 to AC in order to be able to use evasion?