Pros: Very well designed, great warrenty, very quiet on lower settings.
Cons: A little pricey both to purchase and maintain
The Defender is an excellent product from what I've seen. HEPA cleans down to .3 microns, Defender down to .1. It's also FDA certified as a Class 2 medical device.
The claims are that you need 1 for each level of your house, but they're only rated to clean 17,000 ft^3. If you do the math, you'll probably find that's a somewhat small 1 level house.
The charcoal filter will pull odors and, supposedly, some gasses out of the air but needs to be changed every 6 months.
The main filter, on the other hand, only needs to be changed every year and this is mainly to maintain the warranty. Go over a year without ordering one and the warranty will be voided.
I've only run into 1 older defender and, despite their claims of extreme durability, it sounded like the motor was going out. This wouldn't have been a problem, but for the fact that the filter had not been changed for 1.5 years.
The filters, BTW, run $99 and the charcoal filters run 26, so you'll be spending 151/year on maintenance.
It does an impressive job at cleaning out odors and dust, but tends to leave a room/home smelling somewhat strange, most people aren't sure if it's a good or bad smell. If you demo it, they'll likely tell you it's just that you've never really smelled 'CLEAN' air before, which is likely true.
Anyone with asthma or bad allergies would definitely benefit from use of the defender and it's small and light enough to take with you on trips.
There are 3 speed settings, the first is almost silent, the second a little noisy but tollerable, the third should only be used while no one's in the house as it almost sounds like a jet flying over head.
The best thing I've seen about this product is the duel lifetime warranty. You put your name and your youngest child/grand-child's name on the warranty and it covers everything including motor replacements. This, of course, is commensurate on your changing the primary filter every year (the charcoal filter does not 'HAVE' to be used/changed, but without it, odors and some smoke will go right through the machine).
Initial price will be 999, they'll offer 200 off for some reason or other (if buying with their other product, (the majestic) they'll only offer 200 off on the package). From there, you might be able to talk them down a bit. Generally the sales rep will make a $75 commission.