Well, I said I would not comment on what my issues are, but I changed my mind.
For starts, I'd trade a bunch of plastic if they would just get rid of the self propelled set up. Its just another area prone to failure. I don't know about anyone else, but I just seem to see them on ebay with busted transmissions, and other forum members comment on their failure too.
I think it would be just fine if they ditched some of the tools. Most people don't seem to use them.
I'd love to see some of the 60s era design concepts tried out. Did you guys know that there is a patent floating around for a clean air Kirby, and the patent has been around for something like 40 years? Now that would be different!