Having posted quite a bit here in the last 48 hours, I could be accused of defending the Cr-48 and future Chromebooks. However, I want to make sure everyone understands something about a Chromebook on Day 1 and beyond. Even if "the offline feature" for Gmail, Docs and Calendar aren't there on June 15th, you will have the feature on your Chromebook immediately after the feature is released by simply powering on your Chromebook. It's not like the Windows/Linux approach where new copies of those apps have to be downloaded and installed or a lengthy OS update has to be done.
Clearly, if the feature isn't available on June 15th and you have some "disqualifying type of work" to do on the 16th, the trusty laptop will have to go to work.