1. Terrible name
2. Theres no reason to keep to C-style syntax
3. go <function> is a nice feature
4. Control structures add nothing new and just seem generally underwhelming to me
5. The built-in data types are an improvement over a lot of languages, but are underwhelming when compared to something like Clojure, Haskell, OCaml or Factor
6. Channels are a great way of dealing with mutable data in a concurrent environment, but I'm not convinced they're enough
7. Slices and pointers without arithmetic are a good idea
8. The interface system seems like an interesting idea
9. I'm not sure I understand how this is to be a "systems language", especially when they say that its impossible to do manual memory management
10. Lack of things I like: lisp-like macros, closures, pattern matching, parametric types, dataflow constructs, iterators, list comprehension..
Though I personally don't like the syntax very much, it is certainly familiar and easy enough to pick up, so I imagine this will be useful to a lot of people. I think Go is an interesting experiment which will, hopefully, lead to some more powerful and interesting languages, but I cant see myself ever using Go itself.
Its nice to see a C-like language take concurrency more seriously, but after having used Clojure a lot over the past month or two, it just doesn't really seem so concurrency oriented to me.