Google’s GMail has always used the secure https: protocol to protect logins, but it would allow you to switch to an insecure http: session after you were connected. While this can speed things up, it’s potentially a problem for those of us who are on-the-go: unencrypted mail traffic can be snooped on by anyone in WiFi range of your laptop.
That’s why its nice to see the new “Browser Connection” item in GMail’s settings; you can use this to force all of your GMail sessions to use https: throughout, no matter how you get there. This may cause a problem with some applications like Gmail for mobile, but there are workarounds. If you’re the mobile sort of web worker, you should definitely turn this setting on. Check it even if you’re deskbound: on my account the new setting defaulted to https:-only.