With the Open Realty CMS they somewhat avoid the issue of having user input in their search by providing specific fields that return results and match up to specific fields in their database.

It makes sense really, and simplifies the back end a great deal.

What would you do to change it, or make it more flexible or tailored to your needs?

I think theirs is a two step search, you pick the overall category, then you select your preferences in that category and get the results that fit those preferences.