Go code itself is much faster than any dynamic language. But many Go libraries (like regex or http) are very immature and horribly slow, as is the garbage collector, which is the reason for the bad averages in the alioth shootout. Also, there are many well known compiler optimizations that haven't been implemented yet (e.g. optimizing away bounds checking where possible). The stated goal of Go's creators is that Go should be around 20% slower than C.

It's probably a stretch but considering the speed difference between RAM and the harddisk, real life speed of an app has a very close inverse relationship to memory usage. Go uses very little memory, and I don't just mean the runtime itself. Contrary to Java it doesn't treat everything (other than primitive types) as reference types, which hugely reduces the number of pointers.

I think Go is very promising. It's going to be very fast, it's very memory efficient, and it makes massive parallelism incredibly simple. It greately reduces the pain and inflexibility of statically typed languages through type inference and after the fact interface conformance (or whatever the proper name for that feature is)