We bought one with our new furnace this spring. It's a Honeywell which is supposed to be a good brand. The unit is not tough to clean, a couple of filters to pull out and hose off and then a big metal filter system which you can toss in the dishwasher. The unit definitely does work as we seem to have much less dust in the air.
Depending on your furnace configuration it might be tough to install. The guy who put our furnace in said it would be cheaper to do it now before the new furnace gets installed as the air filter sits in front of the furnace.
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