Raw Measurements

1000 iterations, 10000 samples
BitFields Style Pack:   00:00:00.0919455
BitFields Style Unpack: 00:00:00.3154235
BitConverter Pack:      00:00:00.0764927
BitConverter Unpack:    00:00:00.2149990
Direct Packing:         00:00:00.0325352
Direct Unpacking:       00:00:00.2034563
Direct Unpacking Unsafe:00:00:00.2150088
Access and Cast:        00:00:00.0308669
Access and Cast Back:   00:00:00.2004328

100000 iterations, 1000 samples
BitFields Style Pack:   00:00:00.9495634
BitFields Style Unpack: 00:00:03.2461785
BitConverter Pack:      00:00:00.7899617
BitConverter Unpack:    00:00:04.3947272
Direct Packing:         00:00:00.4048323
Direct Unpacking:       00:00:02.1618007
Direct Unpacking Unsafe:00:00:02.2842652
Access and Cast:        00:00:00.3877108
Access and Cast Back:   00:00:02.1245730

1000000 iterations, 30 samples
BitFields Style Pack:   00:00:00.2910572
BitFields Style Unpack: 00:00:02.2447317
BitConverter Pack:      00:00:00.2430286
BitConverter Unpack:    00:00:03.1722101
Direct Packing:         00:00:00.1332875
Direct Unpacking:       00:00:03.4606810
Direct Unpacking Unsafe:00:00:03.2328402
Access and Cast:        00:00:00.1256066
Access and Cast Back:   00:00:03.6251144

10000000 iterations, 10 samples
BitFields Style Pack:   00:00:00.9610064
BitFields Style Unpack: 00:00:12.2807165
BitConverter Pack:      00:00:00.8400908
BitConverter Unpack:    00:00:10.4789114
Direct Packing:         00:00:00.4104641
Direct Unpacking:       00:00:12.5544608
Direct Unpacking Unsafe:00:00:11.2327730
Access and Cast:        00:00:00.4070876
Access and Cast Back:   00:00:10.8822947

Article: http://alangamedev.com/packing-and-unpacking-bits-faster-than-bitconverter/