I only have two Smarthome ToggleLinc dimmers. They are actually older (pre-insteon) ones. I never use them for dimming (intentionally, that is). At some point, I'll probably replace them with Insteon non-dimming switches, so I can use CFL's in those fixtures (recessed spots in my living room ceiling).
I also have one pair of non-dimming pre-insteon ToggleLinc switches (it is actually a "main" switch and a "remote" switch - used to replace a pair of 3-way switches). Those are silent (at least I can't detect a click at all - I don't know if they had a relay, or used solid-state components)
I have four Insteon ToggleLincs, and two Inseton SwitchLincs, all of which have the barely audible click (which doesn't bother me - in fact it is helpful audible confirmation when I'm testing stuff, since four of the switches control outdoor lights)