I own a 450D, and I am very satisfied with the image quality, features, and so on. The only thing that disturbs me is the viewfinder. I can barely see the whole image when looking through it (black blends in near the edges as my eyes focus the image) and as soon as I look through it slightly from the side, e.g. when I'm shooting near the floor, the whole thing gets to be controlled by luck. Manual focus is almost impossible to get right — especially with the crappy focus ring on the kit lens (it's slightly better with the 60mm/2.8). Later, when I view the photos on my PC, I can see details that I haven't noticed at all while using the viewfinder and therefore did not have control of.
Am I the only one having these problems? Is there any possibility to improve my viewfinder's image without buying a new camera? And last but not least, which cameras do have good, big viewfinders? Does it have something to do with the size of the sensor?