We use 2 because we have 2 cats and the person who feeds them tends to be a bit erratic and forgets to come at their usual mealtimes.
We have one circular one with 6 sections which we fill with dried food. We set it to open 3 times a day, at times when they might be hungry. The person coming in only needs to refill it and restart it (one button to press) every 2 days. It's a little tricky to set initially but the times don't need to be reset unless it's switched off. The interior rotates, so uneaten food goes back under the cover when it moves on.
We also have one with 2 sections that takes an ice pack to keep wet food fresh. It's fairly easy to set and we usually fill the sections and set it to open at times different from the round one. The person coming in would need to replace the icepack, especially in warm weather.
We've been away for a couple of weeks at a time and the cats have been fine. They've also survived with just the automatic feeders for a weekend.
They give us peace of mind that there is something for the cats to eat if the person doesn't turn up for some reason.