When I was working in finance I probably used most of the stuff I learnt from undergrad CS (concurrency theory, network protocols, information theory, complexit

When I was working in finance I probably used most of the stuff I learnt from undergrad CS (concurrency theory, network protocols, information theory, complexity theory). It's not often I had to do stuff that pushed at the edge of CS (except maybe with lock-free algo design where industry is ahead of academia) but I'd often need to use my CS training to figure out clever ways to apply standard techniques. In the startup world I've not used my CS knowledge as much, but am starting to do some data-mining stuff which is more theory heavy.