I'm a financial programmer. I sometimes work with some of the quant developers, but I'm not a quant developer myself.
You basically find quant developers wherever you find quants and lots of data to process, and the job is going to look and feel different depending on the desk/group you support.
Our firm's research division has an institutional securities risk and pricing service, and we have a number of quants who work on portfolio modeling and a number of quantitative developers to help them. These guys generally have pretty nice and relaxed lives and deal with a lot of correlation and portfolio optimization work. Typically, the quants will give them a series of mathematical operations to perform and they will turn that into
C++ code.
We also have product-specific quantitative developers. Most of these guys sit on the trading floor and work on the pricing engines and sometimes proprietary trading systems. Their jobs are a bit more stressful.
Financial developers like me spend about 20% of their time working with actual finance stuff and 80% of their time as developers. (In fact, 40% of my time is spent just hunting down bugs) For a quant developer, the percentage increases significantly, but from what I see, they are largely still developers. At a typical large investment bank, much of the financial thinking has already been done before any developer looks at something.
If you're a developer who is also interested in doing quantitative financial work, I would recommend looking at the smaller firms where some of these roles (like quant and quantitative developer) start to merge a little more.