I have a dyson but it's so heavy that I find doing the stairs (plus carting it up and down stairs) pretty difficult. I'm going to invest in an "upstairs" vacuum soon. Hopefully a G-Tech Air Ram since they're supposed to be lightweight. My frozen shoulder is really painful with hoovering.
We went to an Oreck store and tries some different ones out. They even had a brand from Europe that was more expensive, and better, but was too heavy for me. Living in a 1-story ranch with only 3 carpeted rooms, laminate living area and tiled kitchen, we didn't need anything but the basic, that was light enough to push (lifting limit of 5 lb) for me. I went on Amazon and got the Oreck XL Commercial vacuum. No houses or attachments, but it flattens to go under furniture and beds. It's perfect and takes little effort from me. The store will service and clean it once a year for its lifetime.
I have a Shark. And loves it!! It's basically self propelled but not so much that it drags you around the room and it cleans excellent. I actually ordered it off of the infomercial. It was expensive, but I made monthly payments on it, and it was SO worth it.