Not sure where others look, but I do look at the classifieds on AO, it's just a lot of the descriptions are really lacking and some don't have photos, maybe this is because of personal MB usage.
Pistonheads search engine is much better than it used to be, but it's still no good for me when I want to narrow my search. For me, Autotrader is way better for search parameters, Ebay works well too. I think my only complaint would be that the cars i want are over my budget, I'm not sure who's fault that is.
GT 3.2 V6 - Q2, KONI FSD & EIBACH PROKIT, GTA REMAP, MICHELLIN PS3's, BMC CDA
159 SW 2.4JTDM TI - ALFATUNED, WIZARD BACK BOXES, KW V3 COILOVERS, NOKIAN WR A3/MICHELLIN PS3, PCA DYNAMICS ALIGNMENT.