I love how you can all of a sudden see the tiny details. The fruit basket Zorn offers to Riker, for example. On DVD, I could only clearly make out the bananas. Now you can see tomatoes, grapes and an orange as well.
Or the data file about Kahlest in "Sins of the father". Here's what we got to see on DVD:
and here on Blu-ray:
(This is not a screencap, I photographed my TV for that shot...)
We, at Memory Alpha, will have lots of work, once the Blu-rays are released... :-)