i would tend to agree with the last part of your post, "manual/doc for 3.x isn't ready yet"
honestly though. with such a complete rewrite and a pwnage one at that... its probably going to take some time before even basic documentation is fully written, let alone advanced feature data, and then finally skinning and hooks etc...
i would like to express personally my hope that "damn good documentation" comes within a reasonable time frame. i know SMF 2.0.x series that is in the works, has little documentation. (if i recall, they are actually looking for more people to assist with it.)
i could actually see IPB going to the extremes of hiring an entire "team" dedicated to just manuals/faqs/guides/documentation/etc... as in my opinion it is KEY to sucess for a "set and forget forum" and a "tweak and mod to the max" forum.
the more data the community has at hand, the better in the long run. especially to create a strong active mod/skin community!
but enoug of my opinions. to the point.. (i hope) IPS has worked so hard to get IPB3 out, that the product is ahead of the manual so to speak. (or so im assuming)