that will cause you one hell of a work..
since STS-88 (if I remember correctly) when powering up the Boilers (T-00:50:00)
you turn on the OMS and set the OMS actions switches to ARM\PRESS.
I personally believe that you Checklist and an absolute necessity, yet it's only a reference - not a bible.. it helps me know what stage is next - and on Medium Difficulty it's more then enough - because you got the Full checklist on-screen..
furthermore after more the 15 full missions, I remember most of the steps I even know where I can cut stages and do two or three steps on the same time. (usually is the KU-band, Star-tracker, fuel-cell, GPS on launch and KU-Band and Star-tracker on De-orbit)
next up is running all the missions again on Hard, then I'll let you know who important it is to complete the checklist..