How Important is SEO for an Agent's Site?

I have a Realtor friend who is developing his first site, and he is struggling to balance creativity, usefulness, and SEO features.
I recently read on another blog that for agents, perhaps sacrificing SEO in order to give customers what they want up front - access to listing searches - is more important, as it will bring customers back again and again. We all know that sites that feature great search categories but very little text are difficult to optimize, but sites that feature tons of keyword rich text might be confusing to customers who just want to see listings. Where is the balance between getting repeat customers and finding new customers? Is it more important to optimize to attract new customers and then let good old fashioned great service keep them coming back?
Of course, for my site www.lockboxdeals.com, since it is a listing service and supported by ads, SEO is one of the most important (and expensive!) priorities I face everyday, so perhaps my opinion is a bit....skewed!
What do you all think? Does it depend on area of the country - for instance, is SEO more important in major metropolitan areas that have international clients? Does the type of brokerage make a difference - independent versus aligned with a Coldwell or other larger firm? Does a creative site bring more visitors than a site that is functional but similar to a lot of others?