On Tue, Jan 29, 2013 at 2:15 PM, Ganesh Sittampalam
tl;dr: I'm planning on removing the String instances from the HTTP package. This is likely to break code. Obviously it will involve a major version bump.
The basic reason is that this instance is rather broken in itself. A String ought to represent Unicode data, but the HTTP wire format is bytes, and HTTP makes no attempt to handle encoding.
This was discussed on the libraries@ list a while back, but I'm happy to discuss further if there's a general feeling that this is a bad thing to do:
http://www.haskell.org/pipermail/libraries/2012-September/018426.html
I will probably upload the new version in a week or two.
I think it's the right thing to do. Providing a little upgrade guide should help things to go smoother.