I've read the manual cover to cover about 5 times now and would be more than happy to try and answer anyone's questions.
Is that the 80 page Manual as supplied, or the downloaded >230 page PDF manual?!!
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I've had my D5100 since January (my first DSLR, from a pocket CyberShot!), I've not really had a good session at a specific event, but have taken quite a few (300+) test shots out and about locally.
My verdict - I need practice and experience!
There is loads to learn about 'photography in general' and then I can start to get the best from my camera. I love the camera, and I really appreciate the potential of it. This is why I get quite frustrated at the moment after taking about 30-40 shots of something, bracketing and trying various combinations of settings, and not quite hitting the result I was looking for!
It's gradually starting to make sense though and I am starting to remember more. I don't like shooting in Auto mode unless I need to get a shot there and then without fiddling with settings, but otherwise I try to shoot Manual where I can - I just want to be able to take photos that I have captured myself, and not just by letting the camera capturing it for me by pointing it in a general direction and pressing the shutter button!
ISO vs light vs aperture vs shutter speed = a lot to consider. Then there are noise reduction, focus options, lighting effects (D lighting) and many other settings to play with too.
So far I've shot mainly landscapes, sunrise/sunset, and the moon! Mainly tripod stuff, but I want to learn to get a sharp shot hand-held too. I can't seem to maintain sharp focus and DOF when hand-held, but I'm getting a little closer when using the tripod.
Plus I've shot (photographed) my children too, but they don't keep still long enough to really practice!
I've got the D5100 with the 18-55 kit lens, plus I got the Nikon 55-300 lens too. I know different lenses achieve different results, and not knowing the potential of my own kit could be causing me to expect more from it than it is capable of. But on the other hand, I probably just need more practice.
So all of my comments above are very general. They do not reflect the D5100, just my personal ability - they would be the same comments whichever camera I had gone for.
I'm very pleased with my choice of camera, I would definitely recommend it at this price range/specification. If I were making the choice again today, I'd still go for this model for my needs. And I've not had any issues with it not working.
The point of all my comments above is that you can't just go and buy a nice camera to get good photos. The point and shoot Auto mode photos are very much better than I am used to, but I know I can achieve much more with this kit with a bit more practice and experience.
And finally (again, not D5100 specific), once you have done all of that, you can then get involved in Post Processing using your favourite software package - there is almost as much skill involved in this than there is in the taking of the photo in the first place!
Shoot RAW, adjust it later - all good fun!!