My 4" is a Thunder Ranch, as well. I was fairly lucky because I seem to have gotten one of the few of them that had a good trigger pull from the factory.
I didn't luck out so well with my 5 1/2" however, as that gun has not got a good pull at all.
Well, great minds think alike, huh?
Mine (in my limited S&W experience) has a pretty nice trigger pull, but it wasn't new either. Great shooter, very accurate. My wife gave it to me for a wedding present. I picked it up for ~$475, looked like it could have been unfired, just had a couple tiny handling marks on it.