But... I do. One ion cannon is, in pretty much every case, literally going to kill 4-8 units before it dies. A few might get through as many as 20-40. And uh, if by "early game" you mean first couple of hours, sure. Most fortified worlds will chew up and spit out player fleets. Once you have a fleet ball worth talking about, then they'll kill a few and get curbstomped by the player forces. Never mind if you use bomber starships, raids, or any of the myriad instakill immune units to kill it.
Eyes are another story, and I think they are a lot better.