Not the guy you were asking, but I'll give my opinion.
At first I wasn't gonna upgrade because these devices are expensive, Broadwell is coming, and so far it's been almost biannual release cycles. But the Surface Pro has been my daily driver since Feb 2013, I don't use any other computer and I haven't bought a tablet since the original iPad.
For an SP2 user, it's basically incremental upgrades but a couple of them will up usability a lot for certain use cases.
Main ones for me are the resolution, which I originally thought was a dumb move because W8 snap looks better in landscape. But then I thought about how I use programs like Excel a lot. The SP2's widescreen resolution means the ribbon takes up a big chunk of the screen. I end up having to hide the ribbon and the taskbar in order to get max screen real estate to display data and it still ends up feeling cramped. If you're using OneNote with a stylus, the resolution also means it feels more like you're writing on a legal pad, instead of a strip of paper.
Another one is the N-Trig digitizer instead of Wacom.
This blog has a good comparison but the basic gist is it's give and take for artists. But I use OneNote a lot and the Wacom has parallax and accuracy issues, especially as you get to the corners, even after doing stuff like 500 point stylus calibrations. The N-Trig digitizer doesn't need calibration and supposedly makes the stylus feel like it bleeds ink from the tip. I can appreciate that.
Another one is the i7 with HD5000 and double the GPU cores of the SP2. I use the SP2 for some gaming so a 10-15% bump would be worth it. Still waiting for benchmarks though because I don't know if the slimmer form factor would cause throttling to kick in faster. If it did, it would be a waste.
And it's annoying that most accessories have to be bought again. I have the SP2 dock, a power cover, and an extra brick so that's another $400 that has to be spent on accessories. It's a lot of $$$ but I'm probably the archetypal user for an SP so I'm all in.