@krellin: Rand is simply less rigorous than Nozick. The OP is well-acquainted with Nozick's arguments, and Rand says nothing about justice not covered in Nozick. In fact, Nozick goes quite a bit further. This is not a criticism of libertarian thinking at large, nor it is necessarily a slight at the quality of Rand's work. Nozick is one of the greatest thinkers of the last several decades.
And, of course, Rand is not "different" from the usual suspects... you can barely wade into any discussion about the morality of modern markets without running into a thicket of Rand acolytes. I daresay there's nothing less unoriginal in this debate than identifying Rand as suggested reading.
You do, however, accurately identify what makes Rand so attractive to so many. Her writings are unequivocal in their conclusions, to say the least. I personally also find them uninteresting, but that is a valid observation. I would argue that, for a reader interesting in exploring questions of justice, you receive a more complete treatment of the issues in a text that considers what happens when their assumptions break down. Rand, to a fault, believed her views were axiomatic.
And hecks, yeah, sure, smart people can be poor writers. And technically incompetent prose can be very appealing to a great many, while very annoying to others. Technically incompetent prose can also convey interesting ideas. All of those things are true. I personally find Ayn Rand's prose and diction particularly bad, to the point where I generally cannot get through a passage of her works without laughing uncontrollably.