If you notice in all of the Scala books (I've read the one by Martin and the One by David Pollak as well), they all seem to push you towards the functional programming model instead of the much more common imperative model.
But you know, there's a problem with that. Not with the language itself, but with the web development side of Scala. There's only certain ways by which you can program with a particular function that accepts a request and returns a response. So, most of the time, I would find myself wasting time thinking "How can I make this more functional?"
Functional programming is really great when you can actually enforce it - When writing algorithms and so forth, but otherwise, you are forced to fallback to this imperative model which sucks, because you have to constantly keep changing your mindset between these two models.
Another downside of Scala is its HUGE syntax. Processing strings? Here's a ten million ways to do it.. (a bit over-exaggerating). Oh and if you chose this way, then you should use this syntax. No, not that one, THIS one. Oh no, not that one, this variation of that one that looks like this.
I've advocated Scala to many HN members here in the past, you can even check out my comments, for instance. But from my experience, I think Scala is an Academic language. But it's superior in its own ways - I just LOVE the concept of avoiding nulls and passing an Option. It's beautiful. But the downside is its huge academic complex syntax. I want to be able to write code which shouldn't reduce my hair count even if I look at it after 6 long months. I don't want to refer to an 800 page book each time I'm confused about something.
That's why I think Go is beautiful. The syntax is just enough to keep it inside your head forever. I fear that as the language matures, this might also evolve into something as complex as Scala, but let's hope not so.
Go isn't a magic bullet though. It has its own downsides, but nothing w.r.t performance or similar. For the most part, it's awesome.
Once you go Go, you never go back.
P.s - I still love Scala as well ;)