I think flash links are perfectly fine as long as you use something like swfobject and render alternate text links as well for the spiders and whatnot

1 main think I think that helps the most since the nature if idx websites is that they are dynamic is that you have seo friendly urls, good 404 fall back with redirection and a good dynamic sitemap to go hand in hand with your listings

I'd say 90% of all realty search sites I've been reviewing fail to follow any kind of structured flow they all seem half baked and rushed with a design flair that trends toward gaudy at best