I am a little late to the party, but I use a surface pro 64 to run my off road navigation. Topo fusion interfaces very well with the touchscreen. Scrolling with your finger is just as expected. Pinch to zoom also works, but does not change scale as quickly as most smartphone map applications. There are a lot of menus which can be hard to hit accurately. The default pen mapping is a little off in the corners of the screen, but I find a finger is mapped accurately all across the screen. There are some ways to improve pen accuracy, but I rarely use the pen.
The USB port is great for the required puck, but I will likely need to run a usb hub to allow for the gps receiver and an external harddrive to be connected together. I only have the 64gb ssd, so I added a 64gb SD card which only contains my map directory. It is currently half full and I only have topo maps (all levels) for the central corridor of Arizona. I have a small amount of b/w aerial photos, but they are more time consuming to acquire for a large area.
On to the quirks: TF will crash out unless power management is set to high performance. I wonder if this is related to the usb port getting its power reduced. The save track feature will also cause the software to crash, but I believe that is related to the newest update and is being worked on now.The software and system runs great in terms of scrolling/3d/etc.
I do not have a vehicle charger, so my trips are limited by the internal battery. I had the system running 4.5 hours with the screen dim (it was at night) which is a little better than I expected. No issues so far after flying down forest service roads at high speed, but I am worried about the large amount of dust the surface is subject to.
So far I am very pleased.
full res screen capture from last night
