ubergeeknz: From recent dealings with real estate agents, the big players won't advertise on Trade Me (it's a boycott of sorts because of the price increase), but the agents we talked to recommended that we did so because it attracts the most buyers.
However with the market as it stands, as a buyer, you really need to check everywhere for listings and "get in quick" as it were.
realestate.co.nz tends to have most of the listings which have been done through RE agents.
Only in Auckland or perhaps Chch. Trust me - the market is pretty slack elsewhere.