Go 1 Beta App Engine SDK now available
groups.google.com
groups.google.com
I've written this now in Erlang, and in Scala, and most recently in Go. It took me way more than a weekend, I'll confess.
The compilation speed is super fast which makes it feel like you are developing with a scripting language as opposed to a statically typed language. I typically edit code, run the tests and correct my errors without any noticeable time lost waiting.
The Go parser and pretty printer are exposed as a libraries in the Go distribution which allows for interesting meta-programming.