"There is no secret sauce!"
- Inside the Black Box: The Simple Truth About Quantitative Trading, by Rishi K.Narang
In this book, which is well worth reading to get a good conceptual overview of the different components of a quant trading system, the author tells about "one of the most successful" quant funds hiring only the best academic researchers and outperforming competitors every year. However, he claims (by quoting a former employee of the fund if I am not mistaken) that what makes the fund so profitable is the constant and meticulous improvement of every aspect of the system. From technological aspects such as hardware and software platforms, to extremely well researched parts of the system which others may not traditionally focus greatly on. Of course, they have a rock solid alpha model, but order execution algorithms, data streams/cleaning processes, and transaction cost models are considered (at least) equally important.
The point being made by the author is in other words that the strategy itself, although naturally very advanced and "top-notch", is merely one part of a very well oiled machinery where extreme focus is put by every single component, to shape something that is bigger than the sums of the individual constituents.