Few months ago I wrote a patch that drastically speeds up encoding and decoding with surrogateescape and surrogatepass error handlers. However it causes 25% regression in decoding some UTF-8 data (U+0100-U+07FF if I remember correct) with strict error handler, so it needs some work. I hope that it is possible to rewrite UTF-8 decoder so that avoid a regression. The patch was postponed until 3.5 is released. In any case the patch is large and complex enough to be new feature that can appear only in 3.6.