And a bad trigger won't help the best barrel out there... I can't tell if you actually like AR's or are trying to join the bolt only club.
I haven't tried the SSA-E mainly because I'm content with my G2S's, all 5 of them. I have in the past used Jewel, RRNM, Bushmaster, Millazzo, CMC and a few others out there but I like the G2S. It's got a clean break, fast lock time, won't break the bank and is as reliable as anything else out there without anything to come loose, break or wear. I can't say that for the RR, BM or Jewel for that matter.
I'm kind of indifferent to ARs even though I own three (.223/5.56, .300BLK and .308W). Much prefer bolts for most of my needs as I hate chasing brass and don't care for having a brass catcher attached to my rifle.
But that doesn't have much to do with my questions about AR triggers I've already swapped one out for a Ruger Elite 452. Would a Giessele really do anything for me? I'm not convinced.