Couldnít agree with you more Ė very disappointing that the F100 lacks both mirror-lock and pre-fire mirror-up. Undoubtedly that feature was used to push buyers to the F5. The F100 has a cable-release receptacle in the form of a 10-pin socket. Compatible cables include the MC-20, MC30 and MC-36. There are other less expensive after-market 10-pin cable releases available.
I havenít kept careful notes when shooting my F100 but cannot recall sharpness being compromised at the critical range of shutter speeds (1/60 to Ĺ) under normal shooting conditions, though Iíve not done any high magnification or super-telephoto shooting at those speeds either. I canít help but think that mirror vibration would eventually affect sharpness under high-mag and super-tele usage. It would be helpful to hear about your results. Perhaps Nikon can tweek the software in order to provide pre-fire mirror-up when using the self timer. They can tweek it for other things such as leaving the film leader out when rewinding.