Garett Rogers found a pretty cool feature that he has available in his GMail account. What is that feature? Voice chat! The bad part is that the feature isn’t exactly what you think. Clicking the button will open a Google Talk voice conversation window with the individual. Unfortunately at this point they do not have voice capabilities directly integrated in GMail.
If you and the person you want to talk with don’t have Google Talk installed then I imagine the button won’t be available to you. It may make things a little easier but I’ll be really impressed when there is not need for Google Talk to use the voice communications. I’m sure they’re working on it we just need to give them some time.