This is more about framed IDX solutions vs non-framed solutions but I figured most people would be searching for company comparisons based on listing integration in WordPress.
Recently we got hired to recreate a site that utilized IDX Broker's framed listings feed and the outcome was a very happy customer. They were concerned when they went to their new site that they paid thousands of dollars for and saw that when they clicked on property search it was no longer their website in the URL bar of their browser.
On the IDX Broker site they actually link back to their site for this portion to maximize their own SEO rather than the customer's. While the typical user never notices they leave the site because the themes match on both sides of this, search engines definitely do and the result is absolutely no SEO value in any of the properties displayed on the site.
When they hired us to create the site they made it clear that they liked the way their site looked but didn't like that it was very hard to manage their site. We kept everything looking similar but polished it up and made some great additions like map search, integrated testimonials, sold properties management, and an integrated blog that automatically pulls relevant posts from the corporate blog.
To view the live site, visit www.behrteam.com