I have a Master's degree in CS from UW's Professional Master's program. I also had an undergraduate degree in Computer Engineering from a different school in the east coast.
I recommend you get a Master's degree from UW for 2 reasons: 1. You'll learn a lot. I certainly did. You'll meet smart, driven engineers from other tech companies in Seattle. UW's program is challenging and will push you as long as you're engaged. 2. Depending on how you branch out in your career, employers may prefer someone with a hard science background, or at least will give them an edge when hiring. If you have taken an OS course, you'll be that much better an engineer anyway along with being able to put it on your resume.