The point is that fields is guaranteed to keep working the way it does. That it uses pseudohashes is an implementation detail you are not supposed to care about.

Yeah I realise that :-)

The point I was trying to make was that right now fields are implemented using pseudo-hashes. Since pseudo-hashes have problems that I want to avoid I won't be using fields until they're implemented using restricted hashes (or whatever) and the new release has been out enough for the bugs to have been stomped on.