I had a custom IDX built for my site. This was a pain in the butt because the Sarasota Board of Realtors is very protective of their data. I had to jump through a hundred hoops. What I do not like is that the data file given to my IDX provider does not have multiple photos or realtor remarks. So the information is very limited.
One thing that does work well is that when people go to my MLS search page their search is saved. They are automatically set up on a daily property email system with their saved search. This and a phone call is how the relationship gets started. Although, I have been lazy with the phone calls lately.
In the past I used Soar Net. I have a site with them but it has flaws -
www.mlssarasotaflorida.com. They were one of the original VOW systems, however they are not building anymore sites.