As with the previous poster, at this point; I'm not a fanboy of any of the brands above. I have owned Canon and Sony products in the past; but not so much in digital photography products.
I was going to buy the EOS 7D last Christmas since it was highly recommended as the best all-rounder. In terms of image quality; the 7D does it better than the Sony A77. But since the A77 is the newest out of the three mentioned since it was released in August 2011, I myself ended up buying one from that result only because I myself did not want to join the common mainstream Nikon or Canon SLR range.
The Sony Alpha A77 is not a DSLR, due to its advertising and marketing ploy, they call it a DSLT which is incorporated in part to the model, SLT-A77 with all of their other models too from the A55 and so forth.
I bought this camera because I wanted literally all the bells and whistles that the other two cameras did not have.
Obviously the Nikon D7000 has the best quality image sensor by itself, but the 7D and A77 can record High Definition video at 1080 resolutions and even faster on the A77.
Image Stabilisation is found on the A77 only like with all Alphas, whereas the NIkon and the Canon only have that built into the lens. The auto focus on the Sony is very quick, the 12 fps rate is good at first; but this feature wears off if you're not going to be doing any sports and wildlife shooting.
The A77's LCD screen at the back flips out and you can literally turn it in any desired direction and it is one of the best out there on the market.
Now in terms of water resistance, the Canon 7D and the Sony A77 have that feature built into the body; whereas the Nikon D7000 I believe does not.
Furthermore, the A77 is the only camera on the list to have a built-in GPS feature; any photos that you take out doors and if you have this enabled; with good coverage (without too many buildings and high rises), it will give you the latitude and longitude coordinates with your photos and with Sony's proprietary software, it will show the location on a world map of your shots.
Now the Canon 7D and the Nikon 7000 will probably get you better value than the Sony; only because its been around a lot more. The 7D is aging a bit, being more than 4 years old. The Sony A77 is new but the range of lenses available is by far much less than Nikon or Canon combined.
I have hand tested the 7D before making my purchase with the A77, the A77 is slightly bigger, especially wider than the 7D; it feels more robust and the built-in menu system as well as the preset modes seem rather easier to understand more so than the Canon.
Therefore, the Nikon and the Canon are more designed for those who know a great deal about photography and wanting to upgrade to a somewhat mid-level professional entry DSLR. Whereas Sony's intended marketing is for the enthusiasts looking for something that will give you DSLR capabilities but with a built-in dummies guide if so to speak.
To avoid the conflict of interest, I would probably go with the D7000 for best photo quality; if for video and high fps rate, then the Sony A77. The Best battery life type of camera, go with the EOS 7D.
The A77 has the worst battery life because it uses a digital OLEV view finder as opposed to Pentaprism