Well, I finally got the Whirlpool air purifier set up this weekend. It's taller and wider than I expected, but only about 10" thick, so it doesn't take up too much space in the room. It's quiet on the low setting, but a bit nosier on the higher fan settings (which of course are the ones which move the most air through the unit). It has a sleep setting which will automatically run the fan on low for 8 hours, then kick the unit back into a higher fan setting at the end of that period. The settings are easy to change. The main HEPA filter only needs to be changed yearly, but the unit also has a prefilter which needs to be changed/cleaned 3-4 times a year (the unit has two indicator lights which turn on when the prefilter or the HEPA filter needs attention). It may not be a RabbitAir, but so far I'm pleased with its performance (especially given its price).