I picked up a Nikon first, I thought it's what I would buy, it felt awkward and I wasn't all that excited using it nor looking through it and didn't like the groundglass and the markings on it. I also found the buttons and menu counter intuitive and I kind of put it down and stared at it for a minute before the salesman said maybe I might like to look at something else and that something else was a Canon, I knew they were popular but I'd been a Nikon shooter with film for a very long time and was loyal.
The canon fit right comfortably in my hands, I went ahhhhh when I put my eye up to the eyepiece and from there on everything felt more intuitive and I left the store with a Canon and L lens and have never regretted it.
I have since shot my friends 300D and have the same issues and all the crap I see on the groundglass (lines for framing focus squares etc. ) are extremely irritating to the point of distraction. I don't like using it, I feel uncomfortable using it but it takes great photos.
But there is nothing that excites me more than the MKIII to use, it's not a camera I sit back, look at it and think about how wonderful it is, it's a camera I see it, I right away pick it up and shoot something, even if it's just my sink, okay I may open or close the curtains to make the light look better on the sink but the point is it's a camera that I love using.