Hi,
I haven't read the last couple of pages of this thread, so I apologize if I keep repeating what has already been said. I remember being similarly frustrated a few years back after I had switched from P&S to my first DSLR. The images seemed softer and less colorful, they were flat and lacking contrast, etc. It took me a while to realize that that wasn't the camera's fault, but that it is simply more difficult (but also more rewarding) to operate a DSLR. Moreover, I also realized that, even though some people don't like to hear it, PP work is absolutely necessary. Here are a couple of things that might help you:
- Glass matters. After shooting with my kit lens for a while, I bought a 50mm f/1.8 II. The difference in sharpness is unbelievable.
- PP matters. RAW files absolutely have to be postprocessed. Head over to the PP section of this forum; there's a thread where people post their RAW conversions. I think you will find that in many cases a lot of the final "quality" or "look" (for lack of better words) comes from the conversion, and not the image itself. You will see that many unprocessed files do not look spectacular at all - the conversions, however, often do.
- While the reciprocal rule is a good rule of thumb to eliminate blur, I find that for me I usually need a bit faster shutter speeds to make absolutely sure I don't get blur - I guess I'm a bit clumsy and can't hold my hands too steady. Often, very slight blur might not even be perceived as actual motion blur, especially when you don't look at the picture at 100%. Rather, there is just a slight bit of loss in detail and definition. Maybe that was also one of your problems.
- When focusing, always, and I really do mean always, use the AF point in the center. If sharpness in a particular shot REALLY matters, you might even use LiveView. I always had my first DSLR on automatic AF, and never paid too much attention to it. And, of course, many shots lacked that punchy sharpness people like. It really does make a difference.
- Proper exposure. I assume that goes pretty much without saying, but in case you are not too familiar with the 550D's metering modes (again, I'm not implying you aren't, I just don't know your background), take a look at them. I know that many people like evaluating metering, but I found that I often have to customize it a bit.
I hope that helps.