Don’t know that I love the Roomba, but I like the fact that I’m not around vacuuming 🙂 I need a new one though, they don’t seem to last long enough for me. I set mine up to go 3 times a week and while I have the bumpers/barrier beams (forget the exact name of them) I just shut the door to the bathroom and to the back porch to keep it from meandering in there. It has bumpers so as not to damage anything it runs into like table legs. It will navigate under things – the sofa for instance and come out and go back 4 or 5 times (it has a random pattern) but it hits every inch. My dog just grew accustomed to it-she learned that it was a necessary evil and it hasn’t grabbed her up yet. The upright vacuum cleaner does a number on her though… she hides for hours from it.
The roomba is about 12 inches, it easily goes through chair legs, there might be a chair whose legs are extremely narrowly spaced apart, but for the most part it will go under the chair legs, and it will bump around until it finds its way out from between the legs.
Watching it clean, you will think it is missing great spaces, but let it go, it will go back and get areas it didn’t get.