For my purposes, Go's standard library has proved as complete as Python's (http://docs.python.org/library/index.html) and includes some things that the Python standard library doesn't (e.g., crypto, graphics), all the more impressive IMO considering how relatively young Go is.
1. language designed with good intentions (http://golang.org/doc/go_faq.html#What_is_the_purpose_of_the...)
2. designed and built by a group of veteran system researchers and engineers (ie. not javascript)
3. implementation open sourced from the start: http://code.google.com/p/go/source/browse
4. not overdesigned (http://golang.org/doc/go_faq.html#Design)
5. a real and practical abstraction for multicore computing (http://www.usingcsp.com/cspbook.pdf)
Its success, like most languages, will depend on library support. Here's hoping it catches on.