Successful simmering is definitely dependent on your range. Our old GE electric (it was 28 years old when we remodeled the kitchen 4 years ago) couldn't simmer anything without keeping a close watch on it. The instant you turned your back it would burn, or if you turned the element down the tiniest bit more it wouldn't cook at all. It wasn't a lot of fun to cook on.
The new Frigidaire glasstop we replaced it with will simmer a covered dish for hours without requiring any attention at all. I have a recipe that requires simmering round steak and onions in French dressing for up to 2 hours, and since we got the new range it comes out perfect every time.