I'm a 28 year-old web developer/programmer with 4.5 years of experience, and I'm looking to jump-start my career. I'm trying to decide between self-study and a 1-year master's program in CS at a top school.

I'm currently making 65K in a high cost-of-living area that is NOT a hot spot for technology firms. I code almost exclusively in Ruby/Rails, PHP/CodeIgniter, SQL, and JavaScript. I've slowly gained proficiency with Git. Roughly half the time I am architecting/coding, and half the time I am pounding out HTML/CSS for static brochureware sites. I'd like to make more more money while doing more challenging/interesting work, but I don't know where to start. I have an excellent academic record (math major with many CS credits, 3.9+ GPA), GRE scores, and recommendations, so I am confident that I could be admitted to a great CS master's program. On the other hand, there is the tuition and opportunity cost to consider.

I feel like there are a number of practical languages/tools/skills worth knowing that I could teach myself - shell scripting, .NET, Python, Node.js, MongoDB, natural language processing techniques, etc. That said, it's one thing to read about a subject and another thing to have experience with it, which structured coursework provides. So, on to the concrete questions:

1. What programming skills/knowledge should I develop to increase my earning potential and make me competitive for more interesting jobs?

2. Will a master's degree in CS from a top school help me develop the above skills/knowledge, and if so, is it preferable to self-study (possibly for other reasons, e.g., the degree's value as a credential)?