Initial thoughts :
Big question is what it compiles to. It’s about time we had a programming language that compiles a single program down to parts that run on both server and clients, in a really easy and transparent way.
Building in knowledge of protocols like http and json and making services like twitter at least members of the standard library is a good idea.
Like most programmers, I’m sceptical of the “easy English-like” nature of it. We’ve had plenty of time to learn that what’s hard in programming is the logical thinking not the strange syntax. (Update : See my Quora answer)
But if Dog can become a little-language which makes it easy to configure and administrate social software back-ends then it will be very useful. Particularly if there are ways of compiling the same program down to multiple back-ends (Django, Rails, Chicago Boss etc.)