I went to my aunt's house today for a pre-Labor Day BBQ. She recently, within the last year or so, purchased a camera, after much research and reflection settling on a Canon EOS 50D.
She let me try it out today. I already knew that the mark of a professional-grade camera was the ability to manipulate settings such as metering, shutter, ISO, white balance, etc. without having to go into an LCD menu. The buttons are on the camera body and come in handy when, after you've familiarized yourself with them, you are able to make selections and changes without looking - good for when you're working with a fast-paced environment or subject.
She also purchased an 18-200mm lens to go with the camera body, which means it has a wide-angle to telephoto focal range. So she's working with a great lens.
Anyway, it's very true that you cannot simply pick up someone else's camera and start making magic with it. My handy Nikon has a whole LCD menu screen that tells you just about everything you need to know, and it's extremely easy to toggle back and forth. On my aunt's Canon, there's just a small screen on the top of the body and a dial, so more familiarization than I currently had was required to figure out how to select even simple things, like a slower shutter speed.
When I got back to my camera, I laughed at how relatively lightweight and small it seemed. The Canon is large, sturdy, with obviously thicker casing, and the shutter itself is hardcore - it felt like rocks slamming together compared to mine, really, it did.
All in all, my aunt will be able to do some great things with her camera - there's a reason the Canon series is so loved - but I realized I'm very happy with mine. I love everything I can do with it and the only things I'm planning on spending money on in the forseeable future are lenses.
And maybe a better tripod. And a bigger camera bag. And....