I don't think it is rushed so much as being packed to overflowing with features so that Larian will need to finish stuffing stuff in there a bit after release. It is a big, feature rich game that will easily stand on its own at release, and there's not much reason to wait unless you specifically wanted AI personalities or all the companions (yet these may make it in anyway).
That said it's never a bad idea to wait for a couple patches, unless you find it hard to avoid spoilers on the net. Although if too many people did that it would probably impact on the initial release hype and thus sales (if less people are playing and talking about a game), even if you buy full price a bit later to support worthy companies.
