Well, I never said they aren't good, I just heard the give the most stock like ride. And I guess I assumed by that they won't quite give the handling and decreased body roll that a slightly stiffer spring like the H&R or Neuspeed, but again, I'm just basing that on what I've heard, so I guess I can't say for sure.
About the Eibach's sagging, I'm sure it's not a real common problem, but I do know for a fact that my friends dad had them on his miata and over the years they sagged to over a 3" drop. It got to the point where he had to get rid of them. But that may have been an isolated case.