How accurate are synastry charts?

Out of curiosity, I did a synastry chart between myself and the cap. I've never done one before until someone else mentioned it in one of my topics.

And guess what? Eleven positives and one negative. (I did a chart on two different sites just to be safe, same results).

Opposition Jupiter - Uranus "Negative aspect: An unfavorable union, nothing in common." We have a couple of things in common, but at least it's not as bad as having nothing in common.

And I'm not going to do a synastry chart on future guys I plan to date and use this as a reason to dismiss him in the future based on differences in some chart. I just did it out of curiosity.

But this particular one didn't surprise me. Pretty darn interesting though.

Yea, I dunno how accurate those charts are either. I have tried to do one on some astrology site. It went from predicting something completely harsh to something favorable that was totally contradictory.