I've been using LR4 for less than a year now and JUST discovered that my final image in LR4 looks great when viewed in Lightroom. However, even when exporting at 100% quality, the .jpeg version of the same image when viewed in Finder Photo Viewer looks quite different and less desirable. Any idea why? Now my concern is that the CD's I'm providing my clients with of all the final edited images, don't reflect at all what I intended through LR4. Please help!

[carrrlangas]

Several photo viewers or applications in general are not "Color managed". Microsoft Office Picture Manager is while the Windows Photo Viewer is not for example... Google "color management" for more info.

[Miguel]

I've been using LR4 for less than a year now and JUST discovered that my final image in LR4 looks great when viewed in Lightroom. However, even when exporting at 100% quality, the .jpeg version of the same image when viewed in Finder Photo Viewer looks quite different and less desirable. Any idea why? Now my concern is that the CD's I'm providing my clients with of all the final edited images, don't reflect at all what I intended through LR4. Please help!

That is an interesting problem. I think you are viewing thumbnail files in the Finder which are not color managed, even though just about all Mac apps are via QuickTime. Maybe more facts from you would help. What color space were the LR-exported images in? Same question for your CD images to clients?
Did these files begin in camera as Raw images or jpeg?

M