AWESOME THREAD!
Most of my personal gripes have been covered here already... (ADATs of both the Blackface and XT variety, 3630 comp, Mackie 8-buss, all things Behringer, etc... gotta love being on the supposed-cutting-edge in the early 90's!)
Probably the only relatively recent mistake (circa '04?) was buying a Presonus V-Fire interface for transferring a client's tracks from their Roland VS2480HD machine into my Logic rig... where Presonus, in their infinite and uncanny wisdom, stopped driver development while it was still on the market?!?!?! Seriously, WTF???
They pretty-much lumped themselves in with Behringer for me at that point... never again!