I've got a Neato, as I wanted the D-shape to better get into corners and edges. It doesn't get quite as close as I'd like, but perhaps better than the round ones! I got the pet version as well, because I have lots and lots of long thick hair, and it does pick that up very well, carpets and hard floors alike.
I have a very small, very crowded flat, so he has to live under the sofa, with quite a lot of other furniture around - no clear space like the instructions say. This means that fairly often, he gets confused when starting, and doesn't recognise the floor plan, so I might have to try to start him two or three times. He also doesn't totally reliably make his way back to the charging point afterwards - he gets quite close, but I have to push him back into place. I am sure that none of those would be a problem if you had even just a bit more space around him.
Mine has a floor plan and app, and you can block off where you don't want him to go, which is useful. I have no stairs, so don't know how good he is at avoiding them, but I'm sure it's fine. He goes from floor to carpets OK. But I do find that the edge between floor and carpets doesn't get done as well as I'd like, because depending on the floor plan, he might go back and forth across that edge lots of times in one direction, whereas a human seeing the edge would turn sideways and just do one pass right along the carpet edge instead, even if you then went back to the other direction!
There are several Neato versions, and mine was half price in the Amazon sale. The difference between them is minor - things like whether they have side brushes, whether you can program no-go lines, whether they remember more than one floor plan, etc, so the mid-range seemed fine to me (sometimes they get more features as they upgrade the app, even if they were only available on the top models).
Replacing the filters and brushes is easy, and it is very easy to get the roller out to get all the long hair out of it, which is a problem I've had with so many other hoovers - it's such a hassle taking it all apart, which I have to do so regularly with my hair. This one is pretty easy.