Week 3 Muddiest Point

My muddiest point is more seeking opinions.  Open source software seems amazing, and it's free, and sometimes it's almost just like the commercial version.  For example, I starting playing around with Pixlr for Assignment 2, and it seems very similar to Adobe Photoshop. So why would people pay several hundred dollars for something they can pretty much get for free?  I used Photoshop for years at my old job as a designer, but never purchased a copy for my home PC because it's so pricey.  I guess my question is:  What would it take for open source software to become more popular and take a large chuck of business from traditional software companies?  Feel free to post a comment.