Hey, Rick, I really like "Man in the Mirror"! :)
When we get to the "bottom line," I actually agree with you: We all adhere to that famous Spanish proverb that Rand and Branden were fond of quoting: "Take what you want and pay for it." Which means, in this context: Take what you want from Rand's ideas, and take the responsibility for making them your own, integrating them with your own context of knowledge and experience... and move on. And, in reality, that is what we all do.
But there is legitimacy to the study of intellectual history. And it's quite apart from needing to make "a personal connection to the author," as you suggest. It's certainly not about what Rand ate for breakfast! :)
Everything that exists has a past, a present, and many future implications. It's like that whether we are talking about the computer that I'm typing on, the social system in which we live, or something as abstract as an intellectual system of thought. For example, it's a bit more obvious (to me at least) why a historical study of our current social system would have relevance: Understanding how the current social system became what it is and understanding how it functions today are both helpful if our aim is changing that social system.
For this thread, however, let's focus just on the notion of intellectual history: studying the genesis and evolution of a system of thought---its past, present, and possible future implications. It's of interest to trace the origins of an idea or a system of thought for several reasons:
1. It allows us to situate the ideas in an historical context, which might help us to understand both the relevance and application of those ideas to the specific circumstances in which they were conceived (thus suggesting its possible limitations) as well as the current circumstances to which such ideas might still have relevance. Take Rand's anti-communism: It's of historical interest to relate Rand's anti-communism to the circumstances in which that anti-communism took root---not only as a response to the horrors of Soviet communism, which Rand witnessed and experienced, but also as something much more universally relevant. As Rand said about We the Living: it wasn't just about the strangling, "airtight" environment of communism, but a testament against all forms of collectivism and statism. And it carried more universal implications about the sanctity of the individual.
2. It allows us to trace the cross-fertilization of ideas, which might help us to understand why certain ideas in certain contexts may have meant one (valid) thing, and something quite different when transposed to another context. Take Karl Marx: We know that he was influenced by Feuerbach and Hegel. Surprisingly, however, he accepts a lot of Aristotelian realism and "social ontology." He accepts quite a few "evolutionist" ideas from the Scottish Enlightenment figures (such as Adam Smith, Adam Ferguson, David Hume) as well as quite a few ideas about the power of reason from the French Enlightenment (which was actually far more rationalist, in the bad "constructivist" sense that both Hayek and Rand repudiate). Each of these ideas taken in isolation has very different implications than their attempted integration. It's not enough to condemn Marx outright: Trying to unravel the mess that is Marx's framework helps us to identify precisely where Marx went wrong, what specific threads in the tapestry of his thought are lethal.
3. Thus, the study of intellectual history allows us to learn from the traditions we study: to identify what's right, discard what's wrong, and move on. In other words, it allows us to "take what we want" from the various traditions we study, "and to pay for it," in precisely the way described above.
Just a few things to consider, I think, in justifying the study of ideas and their historical evolution over time: how they were born, what they meant, what they mean, and where they might lead us--logically and empirically.