I wasn't even aware of ILS when I purchased my 642. Then after hearing about it, I researched it a bit and found that failures HAD happened, but were rare. Supposedly, it happened to Massad Ayoob, but that is second hand - never confirmed an actual quote from him.
Is it pretty? Nope. Did I think it would fail on me? Nope. So, why did I remove it? Because, I guess the thought of possible failure, even remote, just festered in my head a while, and in the industry I worked in (telecommunications), you always tried to eliminate every point of failure that you can. So, let's say the odds are 1 in 10,000, is the reliable enough? I don't think I'd fly in a plane if those were the odds. People DO win lotteries with a 10 in a million chance.
If it failed at the range, no big deal - just unlock it. If it failed with a crack-head rushing toward me with a lead pipe - whole different deal. It took me about 30 minutes to remove it (I'm sure it could be done faster, but I was meticulous and didn't want to scar/damage anything). I replaced the hole with a plug that looks "similar" but still pretty obvious with the rest of the frame. That doesn't bother me, really, as I bought it for practical purposes, not aesthetics. Yeah, I'd rather have one that never had the lock to begin with, but I'm not selling it.
Speaking of which, someone mentioned about liability in re-selling if I had removed a safety feature, but not sure how valid that is. And I do believe it was S&W caving to political pressure, though not a law. Also, I agree that they should offer it as a choice, not something you have to remove.