Hi, Simon - I just added support to Data.Text for your new Unicode-based Handle implementation, and I'd like to write some tests. The natural way to do this would be to create Handles that will write to, and read from, ByteStrings. Does any such code exist at the moment? I don't see it in base or bytestring, though all the necessary abstractions appear to be present. Also, the place I hooked into the new I/O machinery was at the next level up from CharBuffer. Because the implementation of CharBuffer isn't abstract, I had no opportunity to put a text array in there, so there's an extra amount of copying that happens when going from byte buffer to char buffer to Text. It's a bit of a shame, but I don't see a way around it at the moment. Would you be interested in trying to remove that extra copy, or is the current interface set in stone? Many thanks for your great work on this, Bryan.