The things that come to mind in a real-estate site would be lots of information about your local area, schools, hospitals, art galleries, museums, points of interest, history of the area etc. really make your area look good.
the only thing I'd add to that is "ease of use" when navigating listings.
I've checked out hot property and it's fine, ezrealty isn't bad, but I'm still kinda preferential towards openrealty. I haven't used it with Joomla but I have with Mambo and there was a bridge for it (I don't know if th ebridge would be Joomla compatible). I found operealty to be very robust and easy to customize. it has several loan calculators built in, listings have automatically generated links to maps (you can choose different map sites for default) and area profiles like yahoo's school and neighborhood profiles.