This has been one of my frustrations (with a language I otherwise love). If you fail to update for a couple of months and then come back your code is broken. I understand and support why they chose to do it this way though.
I think it's pretty neat that they have a tool (gofix) that can walk your code and rewrite it so it works with changes. This is possible in many languages, but it's pretty impressive for one so young to have it. I guess anything that makes it easier for them to make reasonable changes is good for the language long-term.
I work on Go, and just used gofix to update all the Go code at Google. It was just a few command lines to update many, many files. Gofix will make updating much less painful (for me, it already has).
I agree that it's an issue, however it is nice that they aren't simply going to sit on mistakes that need breaking changes to fix. In some respects it's another aspect of the 'beta' culture at google, which is IMHO a good thing - open it up to public use then fix as you go before switching to a stable model.
