Go compilers support two operating systems (Linux, Mac OS X) and three instruction sets. The versions for Linux and Mac are equally capable except that the ARM port does not run on OS X (yet).

There are important differences in the quality of the compilers for the different architectures.

amd64 (a.k.a. x86-64); 6g,6l,6c,6a
The most mature implementation. The compiler has an effective optimizer (registerizer) and generates good code (although gccgo can do noticeably better sometimes).
386 (a.k.a. x86 or x86-32); 8g,8l,8c,8a
Comparable to the amd64 port. Not as well soaked but should be nearly as solid.
arm (a.k.a. ARM); 5g,5l,5c,5a
It's got a couple of outstanding bugs but is improving. Tested against QEMU and an android phone.