No experience with their service department. I just think they're the Gold Standard for home audio. I absolutely love how they sound. I wish I could have afforded them.
I run a set of Linkwitz Orions, which to my ear, sound very much like the Avalon loudspeakers I've heard, so they're my "forever" loudspeaker. The Linkwitz LX521 system would also be in that class. Because they are a DIY system, you are your own service department.