Nothing wrong with cross training. Athletes cross train to help them perform better in their chosen speciality, so should programmers.
I like to dabble in other languages and frameworks - my bread and butter comes from MS, but if I write a little util to automate something for myself at work or do a little side project, I use something different - it helps keep me interested and it helps round out my craft. I don't think losing a little traction on the most up to date MS tech will affect you as much as you think because you will probably be able to transfer your skills and approaches from other environments back to the MS equivalent pretty quickly. If you really are worried, take a few minutes every day at work to bone up on some MS stuff instead of reading that extra HN second page link to a blog post on "the 15 essential things you must do to become super successful" and all the related HN comments :).
On the "cool" aspect - cool is irrelevant if your work is satisfying.