I've uploaded a CVS snapshot of abook yesterday to experimental. Cédric Duval did commit really useful stuff there, like the possibility for user defined fields and views, renaming the custom fields, and lists which can contain a quite big amount of entries.
It would be nice if you could give it some testing and send in feedback about it so that I have more than just my own impression about it for deciding if it's ready to upload to unstable for it making it into the release of etch.
Some things I've noticed so far: You can't use a comma in lists because it is used as field separator. Yes, this needs to get changed, but it is no real regression, because the only list used before was the email addresses and you wasn't able to use it there neither. The date field type isn't yet completely supported — it is planed to have content checking in it, I could think of having flexible display ways for date fields, too. So far it has its reason why it isn't released yet upstream, it has its problem, but I think it is still a great advancement over the current stable release and would make sense to get included in etch. Give it a try and report back, either to me or to the upstream list.