I'm going to start a review of the Necrons. I'll review each unit only regarding the upgrades/transport options of each unit type. Here we go with troops:
Necron Warriors- Although with some downgrades to their "resurrection protocols/we'll be back" and armor save I believe the Warriors to be a good troops choice. The unit size of 5-20 can be adjusted to fit any situation you want be it foot or mechanized. The gauss ability of their weapons threatens all vehicles within 24" with at least being temporarily disabled. The Ghost Ark is a great support vehicle. Filled with Necron Warriors and fitted with broadsiding Gauss Flayer arrays they can lay down some serious firepower (30 shots to one side at 12"). Combined with the ability to "heal" models back into the squad the Ark is a formidable support vehicle as well. The Night Scythe has it's own benefits as well. A larger transport capability and the ability to deepstrike can bring a larger threat to bear deep into the enemies deployment area/zone of operation. It also sports heavier weaponry in it's Twin-Linked Tesla Destructor which has the capacity to take down light vehicles or transports so the deploying troops can open up on what's inside. Overall I feel the Warrior to be a good troops choice and would suggest it not be overlooked when considering your army.
Necron Immortals- Right out of the gate the 3+ armor and the heavier strength weapons will draw most Necron players to the Necron Immortal as their standard troop. The Immortals do also have the option of switching their blasters for the Tesla Carbine which can be more effective against horde units. While I agree that this is a bargain upgrade for only 4 points more there are some down points to them. The maximum squad size is only 10 and the only transport option is the Night Scythe which while a good option leaves an open section for 5 more models. That seems somewhat of a waste on the transport side. The other down point is a monetary one. Necron Warriors come 12 for $35(US) and Deathmarks/Immortals go for 5 for $33 that comes down to $2.92 a Warrior and $6.60 an Immortal. In a 2000pt army if you ran 4 units of 10 it would total around $116.80 and the same in Immortals would cost you $264.00!
In the end it really depends on what you want your troop units to do for you. Next I'll focus on the Heavy Support section.