Sometimes this leads to a considerably different flavor as well, which is interesting. Often papers are remembered for their "results", but sometimes the results are only a small part of the paper, and positioned much differently by the original author.
This is the case with Turing, for example. If you go by Turing in the secondary literature, he comes across as very mathematical, formal, rigorous. Which he was, but he was also very aesthetically oriented, playful, and philosophical. Many of his original papers are really quite "weird" in a way, at times even allusive/metaphorical. So you get a bit different view of him if you read the originals. (Due credit: I was reminded of that in Turing's case by this article, which aims to convince humanities scholars that they should read Turing: http://www.furtherfield.org/features/articles/why-arent-we-r...)
This is the case with Turing, for example. If you go by Turing in the secondary literature, he comes across as very mathematical, formal, rigorous. Which he was, but he was also very aesthetically oriented, playful, and philosophical. Many of his original papers are really quite "weird" in a way, at times even allusive/metaphorical. So you get a bit different view of him if you read the originals. (Due credit: I was reminded of that in Turing's case by this article, which aims to convince humanities scholars that they should read Turing: http://www.furtherfield.org/features/articles/why-arent-we-r...)