RE: M4800 and Optimus?
Unfortunately, Optimus will never come to the M4800. It is a fundamental flaw with the interface they used to connect the display to the motherboard (it is only supported by the Nvidia card). There was a support article about it but I don't remember where it is anymore. As seen on the M3800, it is clearly possible to have Optimus support, Dell just for whatever reason chose not to have it
If you are like me and still want a workstation with a fast i7, 32GB RAM, high DPI display, etc. then the only option left is the W540, which should be lighter, have an IPS screen, and (historically) have 2-3x longer battery life. I had a M4800 and returned it due to the lack of Optimus. Unless Dell wants to lose even more customers to a competitor, they better make some changes.
The AC/N 7xxx series is available only through Premiere or phone order, not typical SMB online orders. This is another place where the competitors wins as they still all full customization of their products.