I've installed the original style Atlas drop in board milled frame style in an Intermountain SD-45T. I replaced the stock speaker with one from Tony's (their 'dream speaker' line) which I think sounds better. I've also installed one in a Life-Like Berk with 2 speakers (wired in parallel, the amp in these isn't powerful, series wiring is a definite no-no) in the tender.
The sounds isn't bad. It isn't the fancy prime mover and airhorn specific that the $140 loksound or soundtraxx but it was also $65. The diesel is a generic diesel sound, a number of whistle choices, some of which to me sound completely horrible (as if they were sampled incorrectly or recorder over a phone). Ditto with the steam whistles and bells. All in all, they are decent sounding decoders. I second the suggestion to turn down the sounds. The default for everything is 3 (on a 0 to 3 scale). Simply changing them all to 2's instead helped the sound quality quite a bit, IMHO. I then tweeked some quieter based on my preferences.
I saw the P42 decoder in the Kato at Springfield, but they couldn't get it to work while I was there :-\
