Are E3s worth it?

If your engine runs better after you changed the plugs it's because the plugs are new, not because they have some sort of fancy electrode shape. Any new (with sharp corners on the electrodes) OEM style plug will work just fine.

There's a LOT of total BS out there on product labels. How many of us have a "5 HP" Shop vac with a 110v plug? Can't be true, but the label says it is.