I didn't read the entire manual, Gary. I don't blame you, if you can't use it between November and April! Those are the times when you need it most, because the house is closed up.
If you did go iwth an ERV, you would have to go with the bigger through the wall units which have automatic defrost and can be used year around and will work in double digit subzero tempertures. In trying to make the Panasonic small and unobtrusive by deleting proper defrost mechanisms, they excluded it from markets who have extreme climates.
Down the road, you might want to consider an air forced central heating/cooling system. They can be installed in basements, crawl spaces or attics depending on your architecture. You have the ability to have continuous whole house air movement, filtration and humidification. They also have ultraviolet light systems (which I have) to kill molds and bacteria in the air stream.
In the interim, yes, you probably have made a good investment in the Oreck. It will at least clean out the particulates and the activated charcoal should take out some of the VOC, etc. if you keep the door closed in the room while you are using it.
Hope it works out well for you.