I love Necrons. Always have. Do I think they are overpowered..not really. They have their ups..Monoliths, C'Tans, WBB..but they also have their downs. Like the fact that they have absolutely no options for variance for anything. Everything comes pretty much as-is except Lords..and they have only 2 real options..Staff or Scythe, as an Orb is pretty much mandatory..and most people dont waste points on a Destroyer body or much else in the way of kitting him. There is no real "what gear can I expect to see from Necrons..." like there is with every other army. But on the flip side, Gauss is effective against almost everything, so..no need for alot of variation in weaponry.
The Necron concept and models are pretty straight forward and basic..but the army is one that you dont see a whole lot of, and when you do, you are forced to stop and think about how best to go about beating them based off what your opponent has on the board...be it phase out or turtling up and holding objectives.
The Necron Army needs reworked, without a doubt, and brought inline with 5th Ed. Rules, but it is still an army that, if played right, can be effective using its outdated codex.