He's a fascinating composer, but he can be tough to take. If you're not in the mood, I can easily see patience wearing thin. When I heard a performance of Gran Torso
(1972) a few years ago (his string quartet with an abundance of rustling, scratching sounds) there were a few people either dozing or leaving. I haven't heard it since, but I haven't forgotten it. (This new Arditti release sounds great.)
Last year a couple of guitarists here did Salut für Caudwell
(1977), Lachenmann's "deconstruction of flamenco technique." Basically the musicians tap, stroke, strum and scrape the instruments, in very defined rhythmic patterns. Then I heard Pierre-Laurent Aimard in Guero
(1970), a short work in which the pianist is supposed to scrape the keys with his fingernails. (Aimard used a credit card.) There's no denying that the composer deliberately exploited the piano for many of its "non-pianistic" elements, and of course you would never want to listen to this piece if you were in the mood for say, Brahms.
But in all of these cases, I found myself thinking about the performances for days afterward, and that's worth pondering.