I've upgraded mine with the Ghost Inc. trigger -- and while it's still heavy (we didn't change any springs), it now breaks nearly as cleanly as a 1911. No grunge, no crap, etc. Real improvement!
I was going to do the upgrade myself until I read the AGI guide to the SR9 and then went through the very well-done Ghost Product instruction guide (on their website.) I decided the trigger assembly of the SR9 was too damned complex, with too many tiny grommets and springs and screws for me. Not nearly as simple as a glock, for example. So I paid my gunsmith to do it, but gave him all of the reading materials and instructions. He said the materials kept him from learning some things the hard way .