I wouldn't consider EM (or methyl maltol, which is generally just listed as Maltol in MSDSs, etc.) a sweetener in the same sense that sucralose is. No matter how much you use it will never give you "sugar lips," nor will it give you the the extreme sweetness of much commercial juice.
That said, it does add a sweet note to flavors, and many flavors you use probably already contain a great deal of it, for that reason. There are other compounds like that- vanillin and related compounds also add an impression of sweetness.
I don't think EM is best used as a sweetener, especially because it seems to mute other flavors. It can be used effectively for just that quality though, to round out the rough edges of certain harsh flavors.
You actually need to be a bit careful about adding EM to juice because so many flavors are already loaded with it, and it has odd effects at high percentages. In my experience you can easily wind up with too much EM without actually adding any as an additive, if you stack too many high EM flavors in one recipe. Adding more EM would just make that worse.