crazyoval - Google definitely recognises search result pages as valid pages these days ... you'll often find these on ciao.com and shopping.com results in Google - click on them and you'll find that you are taken to a search results page (often with no valid results -ha!).
The SEO gurus are still debating which urls that include a '?' get spidered correctly, so I'm not saying any of this is guaranteed.
However, the following is an example URL from our website using Smart Search on the term 'bluegrass' :
http://www.smartchoicemusic.com/store/_search.php?page=1&q=bluegrass
If you follow that link you'll see a very keyword-rich results page. If this link had been placed on an open bluegrass forum or similar relevant website, then you can guarantee that the search engines would have ranked that dynamic page pretty well.
If you compare the keyword denisty on that page to the following one, which is the 'Bluegrass' category page in our store then I think you'll see the difference:
http://www.smartchoicemusic.com/store/Bluegrass-c-45.html
Dunno - all I'm saying is that at least using Smart Search this facility is a bit of a side attraction that may or may not work in SEO terms. It has more potential that the out-of-the-box search page to draw in spiders and customers, and if nothing else could be a useful landing page for Google Ads ??