The overall performance improvements in regards of page flipping and opening documents was more than I expected. I have some large PDF documents on my nook and they opened much faster than before. Great!
There much more features added then I would have asked for. My current favorite is
Add highlight or notewhich works in epub and PDF documents. Even if this feature is not bug-free yet (sometimes the cursor movement is not predictable)
Click here for a complete list of improvements.