They initially set an exceptionally high standard for motive control that only now is being equalled. AFAIAC, they're still No. 1 in motor control. Their sounds were always very high quailty, but I would not have accused them of being all that accurate. I have four locomotives, three steam and one GG1 electric, that came with Loksounds. My first was a PCM (now Paragon 2) Y6b from BLI. It was always a star performer, but the LokSond packed it in sometime over the past year. It happened overnight. That loco now has a QSI Titan.
Next came a Trix 2-8-2. Lovely steamer, and of course excellent motor control. Hated the sounds. Don't know who chose them, but they didn't sound like a NYC Mike. It now has an older Tsunami.
Third came a Rivarossi Allegheny H-8. Again, superb motor control, but for Gawd's sakes.....who chose the chuff and whistle??!? In my review for that steamer for MR, I used the descriptor 'chiff', and not a chuff. A large steamer chuffs...it sure as aitch don't 'chiff'. Also, it had a shrill steam chime whistle, and not the hooter that the H-8's had. But that's the sound Hornby chose...they had just bought Rivarossi. It now has a Tsunami.
The last LokSound acquisition is a Trix GG1. What a beauty, just like the Mikado. Peerless motor control. As for the sounds, I think they're pretty darned good! I don't have anything else to go on, but from videos on youtube of the real thing, ESU LokSound did a commendable job on that one.
All that said, you can tune a Tsunami if you don't mind spending the time. I have a slightly hitchy DC BLI J Class 4-8-4 that became an amazing silk purse once I did some digging and learned how to fine tune a Tsunami's motor contrl CV's. Darned cool. Also, besides the well-recieved TCS WOW's, don't overlook the new QSI Titan decoders. They are excellent. In fact, I have tired of the Tsunamis and will only use QSI from now until someone makes a quantum leap in decoder sounds.