If you mean a kibble dispenser, not a good idea, you wouldn't have much of an idea if he's eating or not, or when he's eaten how much. You want to avoid excercising him right before, and for about 3 hours after he's eaten a meal.
If it's an automatic timed feeder, you also don't have an idea of how he's eating really.
I feed raw and it takes me about 3 minutes to feed all three dogs, I pull out some frozen for them in the morning, and at bedtime/dinnertime they go in their crates while I add supplements on top and feed them. In the morning I just give the bowls a quick wash and put their dinner in. If you're doing kibble it's even quicker and not much work.
I don't feed them on a 'set' time either, if we go out they might not eat till 11 at night, or I'll feed them at 2 in the afternoon before we go somewhere.
Yeah, it takes me literally 10 seconds to scoop food into my dog's bowl twice a day. Maybe 1 minute if I decide to add water or something else to it. I wouldn't bother with a feeder. It's best to do it yourself so you can make sure your dog is eating the right amount at the right times and you can notice if he loses his appetite, which can be a sign of illness.
I never leave food down. I've got three dogs, one of whom has a history of being viciously food aggressive, another who will eat eat eat until she explodes, and another who will let the other dogs have her food if they want it. Plus since the Shiba gets raw foods, that would just be nasty.
There is no way to tell how much he'd be eating, it can easily attract ants (even into the house), and can go rancid quickly, amongst other things. If you want to use a feeder, go ahead. But if he's got a big appetite, he can easily get fat from eating too much.