If you have an opening in your portfolio for a great stock with solid growth potential and perhaps even a respectable dividend yield, you would do well to give Pfizer (PFE 1.04%) some serious consideration.As with any stock, there are very good reasons to consider buying into Pfizer and also some reasons to take a more cautious stance. Here's a look at some reasons why you might buy -- or not buy -- shares of Pfizer. Pfizer: An introductionWith a recent market value near $133 billion, Pfizer is a pharmaceut ...