I've heard and read many discussions about Thousand Sons just completely nerfed and sucking because they're more expensive and less effective. Why do people think this?
They are actually cheaper than before, still being 23 points each, still Fearless, LD10, AP3 bolters, and the Sorcerer is only 35 points (included in the basic unit cost) and comes with a power, although it has to be a Tzeentch power. I think they could achieve about the same MEQ killing in a round of firing that a Heldrake could, although they don't ignore cover saves like a Heldrake; but they are also scoring units with a Sorcerer HQ, can't be 1-shotted like a Heldrake....The Icon of Flame may be worth it too, for the extra wounds it could maybe do to weaker hordes units, etc.
So I would probably not take more than a single unit, but I think the Sons are still a viable Troops option, maybe even worth a look as an Elites choice, rather than using a Heldrake, seeing as how that gets shot down the 2nd turn it comes in almost every game I play.