Date: 9/23/2008 12:42 am EDT
Using a transition that protects the edge of the tile from being caught and lifted is the most conservative approach. A typical "T" transition will have a "rail" attached to the floor, and then "snaps" in place covering both the carpet and the top of the tile. These are available in a variety of materials including metal, wood, and PVC.
Based on your description, I would recommend using a transition.