I haven’t had to send my Avidynes in for repair so can’t comment on that. I did have an issue I was able to fix in the plane and factory support for that was good. They have a pretty active and helpful forum as well.
FWIW, the Garmin 530w in my rv8 needs to go in and flat rate repair for that is $2300! Turn time is 2 or 3 weeks I think. So keep that in mind when evaluating the Avidynes.