Okay--Yet another thought (and then I promise I'll shut up for a while!).
in reply to Re: Speeding up point-in-polygon -- take two
in thread Speeding up point-in-polygon -- take two
How important are exact results? If somewhat "fuzzy" edges are acceptable, you could use a quadtree, and just insert enough nodes to get the precision you want. Then you'd only need a select statement to determine whether your point is internal to the polygon.
Who intends to stop thinking about this question for at least an hour!