My main question is (I was about to start another thread for this, but hopefully it fits here) is if I use the DSLR in the auto modes it has is there an advantage over a good PnS like the SD800 I had. Will the pictures be noticeably better, cleaner, sharper, whatever, better in some way...?
Also, one last question, with my point and shoot, the main problem I had--and I believe this is a very common problem--but I'm not well read on it--is that the pictures I took outside were always amazing. However, with indoor dark shots the flash would make everything look really white, not natural at all. If I turn off the flash, the pictures come out blurry though, as if maybe the image stabilization requires the flash to work. Is this problem somehow alleviated with fine tuning on a DSLR?
IMO the biggest advantage of DSLRs over P&S is the low light/high ISO performance. With a P&S, you can crank up the ISO (light signal amplification), but the noise gets out of hand pretty quickly. Here is a Canon G9 at 1600 ISO; see the chroma in Bob's suit (don't tell him I took a camera to the concert):
Here is a Canon 40D & EF 70-200 f/2.8 IS at 3200 ISO. Yes there was more light, but the shutter speed is also considerably faster, the concert shot is at 1/50 and this is at 1/250:
The noise in the second shot is much more manageable. Of course, it cost a lot to get that; but there you have it.
And how often do DSLR users go away from auto modes and fine tune all the settings? I would like to learn to do that, but I don't want to start off just taking crappy shots all the time as I'm learning.
Good question. What a lot of folks don't realize is that for most of the era of personal photography, photographers like your parents and your grandparents understood the terms. They understood f-stops and shutter speed and film speed. They used rules of thumb like "sunny 16" and "f/8 and be there". A photographer took his/her time, set the exposure, focused, and squeezed the shutter. I remember my dad with his twin reflex Rolleiflex; it took a minute or so for him to set up the shot, then, "Say cheese!"
It isn't so complicated. If you get a DSLR, do the following exercises. Choose a fixed ISO of 100. Set the camera to Av, and take a shot at f/2.8 (or whatever your smallest f-stop is) and the same shot at f/16, and see the difference in depth of field, in what is in focus. Then set it to Tv, and take shots of passing cars; take a shot at 1/1000 sec, and one at 1/50 sec, and see the difference.
The best book for understanding the use of the controls, of the trinity of ISO, f-stop, and shutter speed, is Brian Peterson's
Understanding Exposure. Without a doubt, it is the clearest explanation of how these settings work together to make your photographs communicate.