Even though it says it is great for houses up to 3500 sq feet, I think you'll be thoroughly disappointed if your house is any bigger than 1500 sq feet.
The suction power isn't that great, and although it seems to work wonderfully in the store, keep in mind that in the store, you are getting suction power straight from the unit. In your home, that suction will have to make its way across another 20-100feet (depending on size of home) of piping.
This I would suggest getting those power units with premium motor and go for the one rated for at least 7-8,000 sq feet. That one is a lot better value. This is likely a 10 year investment into your property, so I don't think you should try and cheap out.