I was home schooled, as were most of my siblings, and I think that it really depends on the parents. Some parents actually teach their kids, spend the time with them, offer some sort of direction, and I think it can really give those kids a great start to life and a positive outlook towards learning.
My parents, on the other hand, didn't really put the effort necessary into teaching us, and as a result I didn't learn to read until I was almost 12, and than only because my mother finally put me into public school. Reading, writing, basic math, history, geography, you name it, I was missing it from my education. My poor 5th and 6th grade teachers had a heck of a time trying to catch me up to the other students. That doesn't do a whole lot for a kid's confidence, when he can see that he is obviously and severely behind academically compared to his peers. I just thought I was stupid. My mom thought I had dyslexia or something. Turns out I just needed someone to sit down with me and actually teach me.
There's also a lot of social development that takes place at school, and most of the time you can tell when a kid is home schooled by the way they interact with people. Or maybe it's just me, coming from that background, I can usually tell when I'm talking to a home schooler, they often have a certain social awkwardness about them. I know I was the same way until I met my wife and she straightened me out. I often had a hard time appropriately regulating the volume of my voice ("do you realize how loudly you're talking?), or knowing when certain things were inappropriate to say under specific social circumstances. And I totally fail at Trivial Pursuit (we didn't watch a lot of TV growing up either.)
Having said all that, I finished my college degree early, graduated with honors, and am a successful software engineer and wannabe entrepreneur. I have a strong hunger to learn, a well developed sense of curiosity, and I have a knack for teaching myself new skills. I don't know if I am who I am because I was home schooled (although you could probably make a pretty good case for it due to my unstructured upbringing), and given my success in life I don't mean to sound unappreciative. It just would have been nice to be able to read a little earlier in life, that's all. And I'm still not very good at math.