What do you consider to be the downsides to liberally using libraries that reduce the amount of code by wrapping the standard lib or that build on top of other libraries? Personally, and I may be wrong as someone still new to Go, it seems to me that the single monolithic repository model that Google uses permeates the whole community and has made adding an external dependency a Big Deal and something you have to carefully consider instead of something you instinctively do.
Because there's no equivalent of npm in Golang, culturally speaking.
IMHO, dependencies should be pulled in for things that would take you weeks to do correctly. Avoid pulling in a dependency for something you can do yourself in 5 minutes. So I would pull in an http library if it actually did the mechanics of http better than the one in the stdlib, but not one that just wrapped it up for me a bit.
For me, that's not a Go thing, that's just an I'm Older Now thing.
Also, snarkily, dependency management is a mess in Go right now; none of us have any dependencies because we can't figure out how to do it. :P That is definitely a hole right now (though it's starting to get plugged in 1.5 with the /vendor directory) and is definitely exacerbated by the core team not being able to use any solution they could provide for the community.
I wrote this library because I didn't want to rewrite those functions every time I started on a new project. I put it online because I figured that I would be useful to others as well.