A gadget that you get to play with whilst doing stuff you hate...
Unless you live in a quite minimalist house, they're not set and forget devices. You spend longer cleaning them, saving them from unfortunate accidents, and generally nursemaiding them than you would for a traditional vacuum cleaner.
But then again, leave them both to their devices and only one will do a useful job
We don't have furniture that the roomba can under (at least not all of it) and because the roomba can't move the furniture there are places that don't get cleaned (until you do it yourself)
I also find that the roomba tends to eat fringes on mats, or at least wants to push them around. If you're foolish enough to leave dangling cables, you may find that your phone is on the floor, possibly attached to a roomba.
Mine is not smart enough to know about doorways leading to other rooms (the newer ones have a sensor that tells them so it won't change rooms before they're clean) so unless you close doors it tends to wander all around the house spending disproportionate amounts of time in the wrong places.
OK, so after you get to know what you should do (largely a case of making sure cords don't dangle and closing doors) it does a remarkably good job. We have recently removed all the carpet in our house (which it cleaned quite well -- especially pet hair) and it does just as good a job on tiles and wood floors.
A weakness it does have is that its batteries die :-( Ours currently runs for a rather short period of time and needs new batteries. I'm certainly going to replace them and I am also thinking of getting the smarter version which can be scheduled to start all by itself.
It doesn't eliminate the need for sweeping or vacuuming, but it can make a remarkable difference without you needing to do the manual labour.
Mechanically they have a few small faults, pet hair in the gearbox is a nasty one, but I think that has been fixed by a brush redesign.
Pets learn to live with it. Cats and dogs learn that it can't climb on chairs, so they ignore it once they realise that. We had a very old dog that realised it couldn't climb on a very thick mat that he slept on, so he just walked over to that whenever it turned on and then watched it clean all around him.
Because they're autonomous they can get themselves into trouble. They will go into a room and nudge a door until they close it. Because they can't get out they will clean until the battery runs out (all the while searching for the recharge station). If they stop just behind the door...
Whilst they don't fall down stairs, they do stop when they detect a wheel has dropped. Sometimes this can be triggered by a thick doormat or a low window sill. They will make a forlorn sound when this happens and wait for you to come and rescue them. However if you go out and they panic while you're out, you are then faced with searching for the damn thing when you get back. It will invariably be in the dark under some heavy piece of furniture where it has never got stuck before (or after).
If it detects that it is full it will also stop, so I generally empty it before I use it. I then put it down in the room I want it to clean, close doors and/or set up the "virtual wall" and start it. These days it only very rarely has any sort of accident, and that's usually because someone has left something stupid on the floor like a spool of wire.
All up, it's neither as effective, nor as fast as vacuuming yourself. However it's not wasting your time, so the duration is of little concern. If you have a modicum of sense you can pretty quickly remove any potential obstacles and leave it to do its job.
