What I like about the Gmail chat option is I can quickly correspond information about a student that I worked one on one with in 6th period SS to the Para that is going to be working with that same student in 7th period Science. I can let her know if I had any behaviors with the student as the student is on a behavior plan. That way, I don't have to find her in the busy hallway and we can keep it between her and I without any students/staff hearing. She can then also chat quickly with me or ask me any questions about the student if need be.
Sometimes I find my colleagues are off campus, and Gmail chat is a very effective tool to keep current with communication and information. It saves both parties a great deal of time in locating information, as well as each other!