The topic of shutter lag on the X1D has attracted some discussion here. To find a basis for comparison for this and other medium format digital cameras I've excavated some of my collection of old Nippon Camera magazines and pulled some medium format camera reviews; their standard test suite has included a shutter lag measurement. I found the following:
Mamiya RZ67 Pro II (7/93): 125.39 ms
Mamiya 7 (8/95): 12 ms
Bronica SQ-B (6/96): 98.6 ms
Hasselblad 503CW (5/97): 81 ms
Pentax 645N (3/98): 103.8 ms
Mamiya 645AF (2/00): 102.8 ms
Mamiya 645E (9/00): 48.6 ms
Also, Imaging Resource has posted numbers for the Pentax 645Z, using their own test method, which may not be directly comparable with the Nippon Camera data:
Shutter lag pre-focused: 112 ms
Shutter lag live view pre-focused: 385 ms
Pentax 645Z Review - Performance
Mamiya RZ67 Pro II (7/93): 125.39 ms
Mamiya 7 (8/95): 12 ms
Bronica SQ-B (6/96): 98.6 ms
Hasselblad 503CW (5/97): 81 ms
Pentax 645N (3/98): 103.8 ms
Mamiya 645AF (2/00): 102.8 ms
Mamiya 645E (9/00): 48.6 ms
Also, Imaging Resource has posted numbers for the Pentax 645Z, using their own test method, which may not be directly comparable with the Nippon Camera data:
Shutter lag pre-focused: 112 ms
Shutter lag live view pre-focused: 385 ms
Pentax 645Z Review - Performance