I was a Philosophy major as an undergrad and became obsessed with the beauty of rigorous argumentation. There I didn't take a single class listed under the Mathematics department and was almost exclusively interested in Ethics.
Now, two years later, I have quit my job to pursue a Masters Degree in Pure Mathematics (after much self-study and a semester of expensive post-baccalaureate work). While I find the subject (and more importantly the process) of Mathematics absolutely beautiful, I feel that my true love will always be for Philosophy.
Still, I feel that studying math has made me a much better critical thinker, and I am tempted to argue that studying Mathematics has made me a better Philosopher as well (although I haven't had time to really test this claim). In particular, the study of Mathematics has taught me mental strategies to (i) grasp concepts which aren't as easily intuitive as those in philosophy, (ii) to be even more concise in my argumentation, and (iii) to feel comfortable introducing suitable notation on my own to simplify my thoughts and get me to the heart of problems.
Do people have experience with (or know of others who have the experience with) studying Mathematics and finding that it contributed positively towards their ability to do philosophy (above and beyond the opportunity cost of actually studying more philosophy)?
Are there any examples of modern professional philosophers who have non-trivial backgrounds in Mathematics?
Would obtaining a Masters in Pure Mathematics improve one's chances of being admitted to Philosophy grad school?