I'm not sure what you mean by "slow". Can you please clarify?
Please don't take this as "you're wrong" or to somehow invalidate your experience. In the two years of running Guix as my main system, the only time I've thought something was slow was in building Chromium from source (which took all night to compile). Everything else I never noticed. Certainly not downloads. Those were fine for me both in the US and in Europe. Your experience contrasts so sharply with mine, I wonder what the difference is?
I don't have exact numbers on hand, and it's not always, but sometimes when I'm downloading binary substitutes it will crawl at 100-300 kb/s. I know my experience isn't unique because I also see people complaining about it on the mailing lists.
Sometimes downloads are fine though. I think it's an issue of load on the servers that will cause downloads to be slow sometimes.
Please don't take this as "you're wrong" or to somehow invalidate your experience. In the two years of running Guix as my main system, the only time I've thought something was slow was in building Chromium from source (which took all night to compile). Everything else I never noticed. Certainly not downloads. Those were fine for me both in the US and in Europe. Your experience contrasts so sharply with mine, I wonder what the difference is?