For a newbie I have to agree that the SM's are the best beginer army. The exception being what Astaroth mentioned. There is this one kid who plays space wolves at one of the stores I play at. That kid went and bought a Land Raider Crusader, and he puts like 5-8 Wolf Gaurd plus his commander in it. His HQ is like 750 points!!! (Some guy told him to do it, I advised him not to, but guess who he listened to) He can't seem to understand why he keeps losing. Maybe it's because there is almost no way in heck that a 750 point command squad can pay for themselves in a 2000 point battle.
That being said, I am a little shaky about two things regarding necrons and newbies.
A.) Dependance on WBB. Right now the necrons are tuff as steel, but that's because all the rest of the players are still figuring out what to make of them. In 6 months they will be just like any other army. We will all have figured out how to deal with the new threat. My concern is that newbies will become depandent on that save roll, thinking much as the guy in my example that his troops are invincible. As we figure out how to get around WBB as many players already have the newbies are gonna get crushed hard.
B.) The necrons require alot of inter-squad support to work well. There is almost no stand alone unit in the Necron Army. Each unit requires the abilities of surrounding units to be effective. Tomb spiders suppport elite units providing a fallback on the WBB rule, the lord supports everyone within 6" with the Resurection Orb, the Monolith can teleport troops, The pariahs are HtH gods but won't take fire very well and cannot WBB. This combined with the relativley short range on Necron weapons makes for a complex force. The success or failure of Necrons lies in micro-manging the details on the Battle field.
SM's units on the other hand can opperate relatively independantly. The No Fear rule means they don't need another unit nearby, and the power armour gives them a decent survivability. Special chapter rules make individual units even more independant. I.E. Long Fang split fire, Dark Angel Intractable and Stubborn (the rule that makes their devastator squads not fall back), BA Death Company, Black Templar vows, The list goes on and on.