Oh, and I almost forgot: rubygems.org serves gems with an invalid Content-Type header, causing Guile's rightfully strict header parser to throw an error about it. Here's to hoping that they fix it and don't blame Guile's standards-compliant HTTP client.
http://help.rubygems.org/discussions/problems/21223-invalid-content-type-header-when-downloading-gem...
http://help.rubygems.org/discussions/problems/21223-invalid-content-type-header-when-downloading-gem...