Midway through, an idea that began as a learner project turned into a startup, 3-6 months turned into 9+, and I'm learning more than I ever have, and about more than just the programming topics I'd planned on.
Meanwhile, I've gone to meetups and startup events (like the Work at a Startup Day), and my personal projects -and my commitment to developing the skills to build them on my own- have been the starting points of lots of conversations with cool people from cool companies, opening doors to opportunities I'd have never had if I'd still been working at a full time gig that my heart wasn't into.
The most important thing for me has been making sure to use my time well. It's easy to squander the time, so it's paramount to have a plan and stick to it. That said, the plan can be pretty flexible since you set the schedule (assuming you don't have dependents limiting that).
My biggest concern is whether I'll be able to go back to a "regular job" after the freedom of working on my own projects on my own schedule. But I'm hoping that I won't have to find out.
Do it!