There are three bin modules you can get for the 500 series.
The standard vacuum bin (brushes up big debris then squeegee vacuums(
http://store.irobot.com/product/index.jsp?productId=3293484&cp=2804606.3358508&ab=CMS_SelectRoomba_500_102308&s=D-StorePrice-IRBT&parentPage=family
The high...
I have a Roomba 530 with AeroVac. It only cleans the top soil off the carpet along with a fair amount of pet hair, but it really is convenient to have.
Family friend of ours, got pressured into buying a second hand Kirby in excess of $1500.
She was a 70 year old widow on a pension.
Department of Fair Trading was called. Nothing they hadn't heard before. She ended up returning the vacuum and getting a full refund.
The buildup of dust in the inner chamber does not inhibit the performance of the machine.
It is not in the path of the airflow... There is some airflow there... But not the primary airflow..
There is no real need to sterilise the cyclone assembly... Its only going to be come a) unsanitary as soon as it is placed in the machine, and b) Average Joe shouldn't be cleaning it themselves...
I don't see the need...
Under normal household use there is not really any need to clean it out IMHO.
I have a DC02 from ages ago... Still working brilliant... Same with my DC15 (which I have put so much dust through).