I recommend looking at
http://www.kenrockwell.com/tech.htmIn particular read his discussions of 'point and shoot' cameras versus SLRs. He is a professional photographer, and uses both, everything from $150 point and shoot cameras up to the top of the line DSLRs.
For many things, you simply cannot beat a point and shoot. The thing is there when you need it, is cheap (so you are not worried so much about damaging it), and will get the job done.
But for some things the DSLR simply cannot be beat. In a nutshell, the DSLR will give you much more flexibility and much more creative control, in a more expensive and delicate piece of hardware that is larger and more difficult to lug around.
Viewfinders:
While the ability to view the image through the sensor obviates some of the benefits of the SLR, the resolution of the back panel LCD is still no where near that of the viewfinder. You simply cannot quickly evaluate things like precise depth of field using that LCD, but you can get it quickly though the viewfinder. The viewfinder works in low light that would take a 30 second integration time to even get an image, etc. There are still many situations where the back panel LCD simply cannot serve as the viewfinder. That said, using the LCD as viewfinder is so useful that it is showing up as a feature on the highest end DSLRs...and is pretty standard on point and shoot cameras. The best quality image sensors are not fast enough to use as the viewfinder system...but when you spend 20K on the sensor, you don't worry about saving the 0.5K on the mirror system
Image quality:
Larger sensors give better image quality. DSLRs have larger sensors and better quality even at lower MP counts. That said, the image quality of a point and shoot is generally good enough for the application. If the only thing that you care about is image quality, then forget digital and go straight to the 4x5 inch view camera with slide film
If you are making photos for web use, then the quality of a point and shoot is more than high enough.
My favorite type of photography is 'ambient light' work, where I take pictures in dark spaces (home at night, theater, outside) without using any additional lighting. I use a Nikon D80 and a 50mm f1.4 'prime' (as opposed to zoom) lens.
For most people and most applications, zoom lenses are more useful and convenient. But zoom lenses are 'slower' and thus mean more situations where you need to use flash or faster ISO.
-Jon
