I have been meaning to get a post out about this very topic, Renaud at SPS Clerics has put some hints and tips together. I think this is a really powerful aspect of the product, with the gatherer automatically detecting item metadata then allowing the administrator to add it to the index, and search across it.
Using Search from SPS on custom column in WSS
Thanks Renaud
Such a pleasure.
And totally agree : Search is such one of the biggest advantage of SPS
so fan of the GET interface and the Search Results WP !!!