At first, I really hated it, thinking it looked like a shitty dye job that'd grown out, but it's really starting to grow on me and I kind of want to do it...
I always thought of balayage as more like really natural looking highlights and ombre is often a lot harsher- more of just a gradient for fun. They are similar though and have overlaps depending on what you do.
I like both, except when they're not blended much. I don't like the stripe kind of look.