click to enlarge, or see it on Flickr
Shutter Speed: 1/200
Focal Length: 55 mm
I think the difference is much more noticeable in monochrome, although, granted, this photo has a pretty limited color palette. This photo is one that is better viewed in full-res, but 1024 pixels wide will certainly be an improvement over 400.
The real cool parts about this photo are Mirror Lockup and Live View. Live View was something I was trying to get away from by upgrading to a DSLR. I thought manual focus could never be as good on a screen with a limited amount of pixels as it is through a real optical viewfinder. Well it turns out in Live View mode, I'm able to zoom into the photo all the way to 100% view, at any area in the frame I want. Because of this, I learned that auto focus does a great job, and manual focus does a better job when the subject isn't moving.
Also, Mirror Lockup has really impressed me. I never thought it would make that much of a difference with camera shake to get the mirror out of the way first. But when you're in really close, or going for maximum sharpness, it makes a world of difference. I was very surprised. Whenever I'm on a tripod and my subject isn't moving (at all... like an inanimate object, not just a person who is holding still), I use both Mirror Lockup and Live View MF now. Together, they work wonders.