Once you sign up to a company like this, you are in their pocket!
If you want to move away from their system do you still have full usage of the site without the search results of your property listings?
Are you able to extract your property listings and take them else where?
Do you have to start all over if you stop using their services?
The best bit of advice is to go for a completely independent website designed by you or a professional website designer, then look at a MLS that has an available property search webkit that you can plug into your site or have your own database (can be quite pricey though).
Things like this company is promoting is too much of a commitment and is a lot of money to pay out for something that you may not have full control over.