Depends what apps you use
Granted I never use this feature but still doesn't hurt having the option.
This ^. While I personally found no use for the feature as I found the split screen size far too small for most functions (hell, I prefer not to browse the web on my iPhone), I don't begrudge other for having the option and finding it useful.
It matters greatly on my note 3. I use split screen on a daily basis. Its one of those duh features you wonder how you got along with after using it.
It matters to me. I've used it on my note 3 and now on my S5. It comes in handy when you want to watch a YouTube video but also browse the Web. Or if you need two an pages open at the same time.
See, plenty find it useful. Just hope neither of you too ever claimed you couldn't browse the web on an iPhone because the screen was too small.