Ya know, Arc Angel, I've about decided you know what you're talking about.
Went back and polished the safety plunger and striker/FP to a near-mirror finish, and it really helped a lot. I now have a 4lb 4oz trigger that breaks pretty cleanly, and here's what it took:
1. Installation of a Ghost Rocket 3.5lb connector.
2. A "25-cent trigger job" polishing session.
3. Replacement of the NY-1 trigger spring with a 6lb trigger spring.
4. Replacement of the FP safety plunger spring with the one from the Ghost spring kit.
5. Polished all bearing surfaces on the safety plunger.
6. Polished all bearing surfaces on the extractor plunger (don't think this helped trigger pull).
7. Polished entire striker/firing pin.
8. Thoroughly cleaned and lightly polished the striker/FP tunnel and safety plunger tunnel.
9. Polished the center rail on the underside of the slide (no relation to trigger pull).
When completed, I oiled it with the ceremonial single-drop of oil per Glock instructions, and reassembled. I now have a pretty decent, crisp 4lb 4oz trigger pull, down from the original 7lb 5oz pull from before. When I got it the gun was stock with the exception of a Ghost 3.5lb drop-in connector.
It's a shame that so much has to be done to get a decent trigger pull on one of these, but it's worth the small effort and expense to do it. Contrast that with H&K's, where there's really nothing one can do to make a good trigger -- their lawyers must get paid better or something.
Anyway, thanks to all for your suggestions and tips!