Like many Nikon camera owners I'm facing the choice of telephoto zoom. After reading numerous reviews and forum members comments I decided to go to camera store and try both lens myself.
Test stand at store #1
http://www.bytephoto.com/photopost/data/500/2486test1.jpg
Test stand at store #2 (No, this is not a liquor store, mainly :-)
http://www.bytephoto.com/photopost/data/500/2486test2.jpg
I think demo 70-200 sample at store #1 was bad because performance at 70 mm was not good and at F6.3 and above auto white balance was off.
All handheld, VR ON, shutter speed from 1/13 sec to 1/160 sec.
NEF to JPG with Nikon Capture straight from camera with default settings (auto tone comp, auto sharpening etc). 100% crops assembled in PS with no post-processing except auto-contrast in Nikon Capture.
70 mm (vs 18-70):
http://www.bytephoto.com/photopost/data/500/248670mm_part1.jpg
http://www.bytephoto.com/photopost/data/500/248670mm_part2.jpg
80 mm:
http://www.bytephoto.com/photopost/data/500/248680mm_part1.jpg
http://www.bytephoto.com/photopost/data/500/248680mm_part2.jpg
105 mm:
http://www.bytephoto.com/photopost/data/500/2486105mm.jpg
200 mm:
http://www.bytephoto.com/photopost/data/500/2486200mm_part1.jpg
http://www.bytephoto.com/photopost/data/500/2486200mm_part2.jpg
http://www.bytephoto.com/photopost/data/500/2486200mm_part3.jpg
http://www.bytephoto.com/photopost/data/500/2486200mm_part4.jpg
300-400 mm (80-400 alone):
http://www.bytephoto.com/photopost/data/500/2486300-400mm.jpg

My observations so far:
1. 80-400 at its sharpest aperture is almost equal and sometimes even sharper than 70-200 at 2.8. 70-200 beats 80-400 at all focal lengths at F4 and above.
2. 80-400 at 300 mm F8 was real surprise. Full size image (no post-process) link below: http://www.bytephoto.com/photopost/data/500/248680-400_at_300_F8_s.jpg;
I think sharpness is excellent (1/20 sec handheld).
3. I couldn't get reasonably sharp picture with 80-400 at 200mm/F8. 80-400 at 200mm was sharpest wide open! (F5.3-5.6). At 105mm F8 again was sharpest.
4. At 400mm 80-400 was not good :-( Soft at all apertures, very prominent chromatic aberrations. In fact I've found 300mm shots more detailed.
5. VR is great. Considering higher ratio of sharp vs blurred pictures I think 70-200's VR works better.
I was leaning towards 80-400 but inconsistent aperture 'sweet spot' at different focal lengths and not good 400mm performance make me thinking of getting 70-200 with 1.7x converter. I'm almost ready to buy my first telephoto but can't test 1.7x converter as it is not available yet in my place.
Feel free to comment and please advise if image quality of 70-200 with 1.7x would be on a par with 80-400 in 200-340 mm range.