Laptops are a must for field work that's for sure but i just don't have enough faith to use them for more than that. A quick live capture... maybe a few quicky edits... but that's about it. Anything else goes back to the workstation.
I've had laptops for years and I'm forever having to get the little things on them repaired. The powercord plug (usually the female side that's inside the machine)... the hinge on the screen... the sticking keyboard buttons... the loosened connections on the usb ports.... the dead batteries..... yadda, yadda, yadda. To me dual screens would just seem to be one more thing to add to the break-down list.