I graduated two years ago with this exact degree from University of Waterloo. My favourite subjects were Quantum Mechanics, General Relativity, and Computer Graphics. Throughout my undergrad I was somewhat hoping to go into game dev to work on graphics or physics engines. I ended up getting a ton of internship experience doing web dev, and now I work at Google. The math degree ended up being more of a hobby, and I'm ok with that. I am pretty lazy and so I found it hard to stick to my guns about utilizing both degrees on the job. You have to be prepared to move a lot, and to pass on very good opportunities. I prefer using my math knowledge for side projects and keeping it from becoming a job, though maybe thats just sour grapes.