In the first place how can you compare a pro series dslr and a beginner dslr?
Seriously I do not regret buying d5100. The reasons are below:
1. It is light, I do not get shoulder aches when I lug it all day long, especially during tour.
2. It got a flip screen which is good when my gf and I want to take our own shots
3. ISO control is good compared to the rest of the nikon dslr series except the pro bodies. It is good enough for me and my daily usage.
4. It is small, I do not need to get big camera bags just to store 1 big body and 2 other lens. I can put my d5100 camera in any bags that I have now.
5. It is so much cheaper than the rest of the nikon dslr except d3100.
6. I use it for my leisure only.
7. Flip screen is also good for low angle ad other awkward angle shots.
8. Lens selection are limited but great, I do not need other lenses currently.
9. Enough for family gatherings and personal gatherings
10. Camera depreciation is not that great if I want to sell next time. Unlike the pro series camera like D3S, it worth $14k now but in 5 years time, it's market value is not even $5k. Last time I used to own a d200 which cost me $2800, in 3 years time, I only manage to sell it at $950.
Agreed, and that's why I got a D5100 for leisure after previously owning a D300. However, to be a fair judge, here are some caveats to owning a D5100 that won't necessarily immediately cross your mind when you compare the D5100 to the D7000 (expands on Reno's point no. 8).
1) D5100 doesn't do matrix metering with older AI-S manual focus lenses. I love MF lenses for two reasons: build quality and price. Good MF lenses like the 105mm f2.8 micro can be found at half price compared to the new 105mm AF-S version. I would normally use MF for macro work so the cheaper AI-S 105mm is the lens I would get. However, this lens won't meter with D5100.
2) No autofocus screw. Ok you all know this already, but do you know that A) AF-S lenses are more expensive than the AF-D counterparts? Therefore you might spend less on the body initially, but you might need to spend more on AF-S lenses later on. B) You miss out on a lot of pretty awesome non AF-S lenses; for e.g. 105mm/135mm F2 DC.
For a beginner photographer who doesn't care about the wide variety of lenses that Nikon has to offer, then the D5100 is perfect for him. But for somebody who would want to explore Nikon's long (and historic) line of lenses, a more advanced body like the D7000 might suit him more.
Other things that annoy me (slightly) in the D5100 that might annoy you too:
3) There is no shutter release priority option for single release mode in the D5100. In other words, when the camera is in AF-S mode (single shutter release mode) the shutter will only be released if there is focus lock and you cannot change this in the option menu. There is only shutter release priority option for AF-C mode in the D5100.
4) Cramped grip. I've got big hands. But obviously better than those mirrorless camera grips.
5) Tiny and dark viewfinder, but it gets the job done regardless.
But even having said all that, I can't agree more with Reno that the D5100 is an extremely value for money camera. It has the same sensor (though not the same AF and metering systems) as the D7000 at nearly half the price. Great flip out screen for playing around (it's really fun to use, trust me). And I don't have to worry about depreciation.