[masfuerte]

You don't simmer for twenty minutes. You simmer for ten and remove it from the heat for the remaining ten. The rice never burns because it is still quite wet when you remove it from the heat. Start with twice as much water as rice (by volume) and it comes out perfectly. I've been cooking rice like this for thirty years and it's always great.

[walthamstow]

That's synchronous cooking. Think of a rice cooker as asynchronous cooking. You turn it on, walk away, come back whenever you're ready and you've got rice waiting for you. It is extremely convenient.