I have an iPad, and I've happily used it with the DTs from a young age, but in very short sharp specific bursts.
So googling nursery rhymes to singalong to when they were babies, for example.
We have a few videos - Peppa, Thomas, DipDap - on it, which are a godsend when unexpectedly delayed. Earlier this summer I was involoved in an RTA and stuck at the side of the road, with two 3yos strapped into carseats in an unsafe vehicle for 1 HOUR 45 MINUTES. The only way we got through it was by watching back to back tv on the iPad. I uttered a little prayer to Steve Jobs that day.
I also have a sketch pad app which they love drawing with, and has the great advantage of being mess free in waiting rooms or restaurants.
There are a couple of brilliant CBeebies apps - an interactive story telling one, nad a games one which lets you design and feed your very own dinosaur.
I also use it for googling stuff - so the other day DS was asking me about Red Arrows (he'd seen them in the summer for real) and I was able to call up some pictures to draw one with crayons with him from, and watch some videos of their stunts. Used like this I htink they're brilliant, and I am sometimes tempted to buy a cheap/second hand one 'for' the kids so I don't have to be precious about the screen getting scratched on mine.
BUT we only use it occasionally as they are VERY addictive, getting DS to put it away after he's been watching something that gives him instant gratification (like You Tube 'trains') is hard. And it's mine. They know they can share it, occasionally, if they treat it with respect and are being good.
No way on earth I'd give a 1yo - or tbh under 8yo - their own to use freely.