Bearing members, such as journal bearings, and turbine assemblies for use in high speed, high horsepower applications (e.g., turbochargers, jet engines, internal combustion engines, blowers, steam turbines, compressors, and pumps) including a rotatable shaft, a compressor wheel coupled to the shaft (e.g., at one end), a turbine wheel spaced from the compressor wheel, the turbine wheel also being coupled to the shaft (e.g., at another end), and at least one bearing member having a superhard bearing surface.