Optics play a large role in delivering high quality, sharp pictures. The best proof of a lens' abilities is evident in the image. Specs, benchmark tests and even the brand's heritage are helpful in determining the quality of a lens. Digital cameras offer a wide range of options-from automatic everything to a combination of auto and manual. Assuming you are knowledgeable about f-stops, shutter speed, ISO, white balance, etc., the ability to control these variables will better your chance of getting the image you want.
Some models work better than others.
Again, the proof is in the image. When shooting in single-shot mode, the camera sends each image to the disk after every shot and you can't shoot again until the image has been saved. All else being equal, the ideal is to have both optical and LCD viewing options. The LCD is great because it provides a larger, and often more accurate, viewing area when composing and it allows you to playback your images in-camera so you can check to see if you got the shot you wanted. However, using the LCD as a viewfinder quickly sucks the life out of batteries.