Not having an address really cuts out a lot of people. In a slow market with lots of properties available - not having an address only helps the agency not you. (They want people to call so they can get more listings).
We've just bought a property in NSW and had to fly back and forth from QLD to do it - we only had time to look at a limited number of properties each visit and any that didn't have an address never even made it to our shortlist. We just didn't have time for long convoluted phone calls with agents and we needed to see the property on google maps and nearmap before deciding whether it would be suitable location-wise.
Hope that helps.