My experience with a couple lower end ones and a sheddy dog is that they work well for what they are. Don't expect magic. Expect low effort daily maintenance cleaning that keeps things spiffy. Maybe the higher end ones are significantly better? My bet is that the cleaning isn't all that different since among a product line they largely use the same chassis--there is only so much sweeper/suction/storage they can have.

The one upgrade that would be useful in retrospect is electronic fencing, but it isn't a big deal.