I'm actually in two minds about it as both cameras has their strengths and weaknesses, without a doubt the Fuji X-Pro 1 is an amazing camera (based on what I've seen so far) but until it gets officially released and numerous hands on reviews are made I will hold off in ordering one. The NEX 7 on the other hand is also a fantastic camera but also has it's particular quirks that I'm not too impressed with.
Viewfinders:
I'm a big fan of electronic viewfinders (some people prefer optical, so this will be a matter of personal choice) there will always be an issue of lag but the ability to apply filters (b/w, sepia, etc..) , white balance (sunny, florecent, etc..) and tones (high contrast, low contrast, etc..) directly to the image being shot really does help visualise the image you are trying to capture. The Fuji X Pro 1 has both OVF and EVF, I think this is quite novel idea, however I think that's what it is, a novelty, changing the lenses on the Fuji X Pro 1 will change the magnification value of the OVF (depending on the lens' focal length) via a sliding magnifying glass, that's exactly like an EVF but you also get the WYSIWYG effect with the filters, tones, and white balance. EVFs-wise the NEX 7's EVF is still the one to beat IMO.
Sensor:
Both cameras sport an APS-C sized sensor, The Fuji X Pro 1 has a 16 mp compared to the NEX-7's 24mp. The Fuji X Pro 1's sensor however uses the 6 x 6 colour array pixel set arrangement and does away with the traditional 2 x 2 Bayer system, this reduces moire which lets them omit the anti aliasing filter altogether, the end result is images with no resolution loss. I've seen some of the images taken from the Fuji X Pro 1 in flickr, and all I can say is the IQ on the images surpases
ANY APS-C or FF sensor camera
BAR NONE. The NEX-7's 24mp sensor is no slouch by any means, however there has been reviews stating that it is prone to noise due to the high amount of megapixels. The NEX-7's sensor also has the magenta colour shift issue when used with wide symetrical designed lenses, not sure with the Fuji X Pro-1 on this as it still remains untested. Sensor-wise I'll have to say that so far I like the Fuji Pro x 1's sensor.
Autofocus speed:
N/A, I never use em
Price:
Both cameras cost an arm and a leg, actually the Fuji X Pro 1 is more expensive so it'll cost an arm, a leg, and a kidney.
Lenses:
So far one of the biggest criticism with the NEX series is the selection (this is now changing though) and the quality (with the exception of the Zeiss) of their lenses, while it's not terribly horrible, its nothing to write home about either, I feel that it's difficult to take advantage of the NEX-7's excellent sensor because of the NEX's native lenses. The Fuji X Pro 1 's initial lens selection is mainly composed of primes (this really appeals to me being mainly a prime shooter) with aspherical elements, a redesigned curved aperture blades and a proprietory Fuji super EBC coating that will make the lens very sharp corner to corner, free from CA and barrel distortion. The aperture controls for the lenses are also located in the lenses themselves (which I prefer) as opposed to the NEX-7 which is controlled within the camera. Though I can only speculate on the quality of the Fuji X Pro 1's lenses since I have not personally used them, however I have used Fujinon lenses in the past, and if those lenses were anything to go by, then I can confidently say that we can expect a LOT from the Fuji x Pro 1's lenses.
There are other issues like personal aesthetics such as styling, controls, function, etc.. but this is long enough as it is and I wont make it any longer, I'll just say that this will depend on who's holding the camera, either one will be fine with me as I find both have their merits and flaws.
With that said, I'll be taking delivery of my NEX-7 this week (hopefully) and I'll wait until the Fuji X Pro 1 becomes available for everyone one to have a 'real world' hands on review on it. This should give me more info and help me decide if I'll go ahead and purchase one or not.
Hopefully my liver will be healthy enough by then so I can sell it on the blackmarket to fund this camera.