Bought this unit in early March from Harvey N with spare filter for tot $394 (was on special) and so far I'm very glad I did. Easy to use, built in timer, 3 speed settings... on LOW its almost soundless, on HIGH gets a bit noisy but it clears the air in a room in 2-3 minutes... there is very little dust accumulation on the furniture since I use that filter.
Retail price of replacement filter is a bit high but unit comes with one filter already in and it should last for well over a year if run for 8-10 hours a day

Got this one for $319 from Harvey Norman store. We live on the busy street and dust an$ pollen are allergens that trouble us since we moved to melbourne. This purifier works well and you can feel a difference in a nicer, cleaner fresher air quality in the room. Oh, it is also very quiet and I love the fact that it had 3 stage air filtering system. Longevity of the filters is more than 7 months and vacuuming the Pre filter every week would extend the life of filters even more.

Purchased for allergies so I bought the larger size. Have been running it o/nite for weeks with our door closed but haven't noticed a lessening of symptoms or any 'air' improvements. There isn't any scientific digital display so we can't really get a HEPA measure of the actual air quality. The fan is definitely working but to us it feels like the room becomes stuffy, not clean and fresh. Will persist but I regret not doing more comparative research as this one feels like a bad purchase. Also worth noting - this unit has a bright blue illuminated LED panel but no sleep mode which is really obtrusive at night in a bedroom.