An iRobot is my choice and does a great job, then I use a handheld rechargeable Dyson on the stairs. Actually I bought a second iRobot on Gumtree so one is upstairs doing the bedrooms, the other one is doing the living areas, while I do the stairs then have a coffee while the robots are finishing their floors. Perfect if you have a bad back...or even if you don't!
The iRobots are not the expensive, programmed models, just the basic 530 so I have to press the 'start' button...not difficult at all, I would never go back to vacuuming the old way, there are better uses of your time. LOL