I think Cointalk along with the other Numismatic Forums that I belong to have had an impact on the way that I collect coins. I used to buy any nicely rainbow toned coin that I could find. Cointalk has shown me that many collectors focus more on strike and surface preservation than luster and eye appeal which is what makes a rainbow toned coin great.
I have learned that a true quality coin must have the correct balance of all of the elements of grading. As a result, I now own coins that I no longer think are great simply due to toning. Here is an example of a coin that really does not meet my standards anymore.

In the end it has made me a more discriminating collector. Not to mention that I think this is the most friendly coin forum out there hands down.