I think the one thing you need to be careful of when you add garden soil to a houseplant mix is bringing any pests inside with your dirt.  That's all you need — a disease or pest going from pot to pot.  I know that they used to suggest sterilizing the garden soil by baking it in the oven.  Personally I've never tried it, and the smell of cooking dirt might be a turnoff anyway.

I find the current potting soil feels like shredded bark.  It may be dark in color, but it doesn't have the small pieces that indicate it really contains anything like compost.  Plus, if you look at the price of the “best” stuff, and compare ingredients with the cheap stuff (just like reading labels on cans in the pantry) I found that the only difference in most cases was the addition of perlite.  Perlite loosens the soil, and it's not cheap.  But double the price??