I have been using it for a factor and value based microcap strategy for the last 4 years and have been beating the market's total return by about 5% on average each year. I trade a relatively small universe, its not really scalable to a large fund.
I stopped applying for "quant" jobs in 2007- everyone wanted a PHD even though I was doing a lot of the same work- I got lucky and landed a job in Options AMM and for awhile was doing both dev work and what I later found out was considered quant work in most other places.
My point being though is they provide a lot of infrastructure that would normally only be available to a very small number of people in banks and the like and those tools are gate-kept to PHDs and those deemed worthy of even getting a look. I don't put my algos in the competition and actually trade them manually so they are likely completely under the radar from quantopian, and aside- they look for very specific characteristics in their algos that mine don't fit. There is opportunity out there though, especially if you are trading in small size (lets say under 5-10M),