I concur. If what you want is a more difficult army, then stay away from Necrons. The truth is that while there are, as always, little tricks and tactics that separate excellent Necron players from the merely competent, to achieve basic proficiency with Necrons (as in, winning about half your games) is practically effortless if you have a strong list. Yes, there are limitations that basically screw you over totally against some opponents, but against some others, the army practically plays itself. This isn't an attack on Necron players by any means--I play Eldar, and will readily admit that the same applies to them, and much, much more so for air cav.
For a more challenging army, you might consider Dark Eldar, IG, any flavour of =][=, or any 'nid army that isn't either Godzilla or 'stealer shock.