Consensus is that it's not particularly effective and easily defeated by simply preventing them from getting a clear straight on unobstructed shot at your face. The biggest threat remains knowledgeable long time casino employees with a long memory for faces and good photo databases searchable by keywords. By the time you've gotten the interest of surveillance so that they are looking for you in their database or running skills checks on you you're likely about to be toast whether the casino has a well functioning FRS system or not.

That does not mean that as hard drives get gigantic and computer processing power gets faster that FRS systems won't get incrementally better over time, particularly at newer casinos which have high definition cameras located at pinch points designed to get good straight on camera shots at everyone walking into the casino. Keep your hat down and sunglasses on until you get to the 21 pit and don't cash out immediately after you play.