What if I don't want to run your version(s) of CentOS/Debian, guys? Hmm? (I hope somebody from there reads this) :)
Still, its a very very interesting offering and something to keep an eye on. I bet nobody here is using it yet because its still early days and the thread devolves into such old classics like "you'll never be able to reach a human at Google" and "they changed up their pricing with Google App Engine that one time and my app was no longer free to run all of a sudden!". Sigh.
I personally think it would be great if you could spin up the same instances on either cloud and load-balance/fail-over as needed/cheapest. Docker makes it doubly exciting.