Michael,
Websites serve multiple purposes, and they are essential in today's market. People who have the means to buy a house have a computer, and they use it. These days, they use it at work. Yellow pages, print ads, and other traditional marketing methods are ancient, blunt objects.
Choose carefully. Ease of use may also limit your capability.
Think like your client or buyer. They are busy. The web allows them to save a lot of time. Serve that mind set.
First, your website is your gateway from your offline advertising and networking to online presence. All of your offline marketing materials should feature your website. Get a domain name that is easy to remember and "type in".
Second, your site serves to display and feature your own listings, and prefereably the local MLS listings as well. Whatever solution you select, it should have that capability, or the capability to add it.
Finally, if you are interested in garnering seach traffic to your site (and you probably should, but suprisingly, many agents ignore this completely), your site must be prepared and structured to get it. It does not happen automatically, and don't assume that your webmaster will do it for you. You need to understand what it's all about and become and engaged participant.
Here's a multi-page document about search engine optimization that was specifically written for real estate professionals, using real estate examples:
Search Engine Optimization Basics For Real Estate-Related Websites I hope it helps.