I have something like 12 BLI steamers from the years 2004-2024. These comprise several types of steamers, some with original QSI decoders, all but two still working. The others have P2 or P4 decoders with no letdowns to date. Some of those steamers were acquired through BLI's refurbished outlet, so second hand really. One of those original Niagaras with a QSI has had a P4 decoder with keep-alive cap installed. My BLI PCM Y6b Mallet lost its LokSound decoder 12 years ago and I had a friend install a QSI Titan, which still runs very well. None of my five or six Soundtraxx Tsunami decoders has failed yet.
I have returned two steamers to BLI for repairs, and both run well to this day. One was at their cost, the other was at mine (I dropped the PCM Y6b and broke off the mount for the front engine. Cost me USD$45 plus shipping, two ways. That was in 2012, so dated info now.
I have a 2004 Challenger in HO from Lionel when they were last in that market. QSI, and it's almost my favourite locomotive. Not heavily detailed, but heavy, all metal, twin speakers, and it's a real workhorse. I also have a Rivarossi Allegheny 2-6-6-6 with Tsunami, and a Rivarossi Heisler with an earlier LokSound. The Heisler is now 9 years old, and the Lionel Challenger is 20, but run very well and reliably.
I had to send back my Rapido H1b 4-6-4 because of a broken gear. There was nothing wrong with the gear, but one of the siderod screws backed out, unbeknownst to me, and when it finally caught on something immovable, it broke the gear. Rapido fixed it and it's back to me, unopened now two weeks.
I have several types of diesels from Rapido, Atlas, and Athearn Genesis. The ones that run most reliably (starting up, moving off, staying on the rails, sounding good, even after two or three years in their boxes) are my Atlas Master Gold FM H24-66 from around 2005/6 with QSI (yes, still working) and in 2017 I picked up what was probably a three/four year old stock Master Silver Classic RS3, also with QSI, and that also still runs very well. I had read, many years before acquiring my first Atlas, that some of them have/had Kato drives in them.....? I seem to recall that all these years later, perhaps erroneously.