I know it is almost certainly too late, but I think a lot of people will
be confused by str.decode() and bytes.encode() (or was that the other
way around)?

Calling the methods str.tobytes() and bytes.tostr() (or nicer,
str.to_bytes() and bytes.to_str()) would be hard to confuse and IMO will
lead to fewer bug reports and complaints once Python 3.0 final comes out.

And there is a kind of precedent in that threading.isDaemon() became
threading.is_daemon() between 30a5 and 30b1.