Yes, Preserve Details (and the addition of the Reduce Noise which is very important) is an advance in upsampling...
The key to successful large upsampling is to start with really good images with good image quality. Anything wrong like camera/subject blur or missed focus will magnify the problems when upsampling. Same deal with noise and good capture sharpening before upsampling. I'll also say that you should upsample before doing substantial retouching...if you retouch first then upsample, you magnify any retouching problems as well.
Also know that after upsampling you may need to do additional creative sharpening and even adding photo grain to increase the micro detail in the upsampled image.
Thanks! Roger re doing the upsample first. Makes perfect sense. I've been using your photo grain technique on some images to very good effect since watching your tutorial on it, so will keep that in mind on these images. Appreciate the come-back.
As a side-note, since I got over my hissy-fit and signed up for CS6 CC, this one feature alone just paid for more than the first year of subscription.