In the 737 you have to be careful during descent as the autopilot will quite happily fly you into the clacker (and overspeed protection if installed, its just an option) in VNAV descent if you put in wrong values (descent wind for example) or if you mishandle the thrust, as thrust is only in HLD. Auto-reversion to speed mode will only occur if you have that particular overspeed option on your plane and then only closely before reaching MMO/VMO.
And i do agree about the Ka-8, was my first single seat airplane
