The new Nitro reader looks like a nice step forward, though PDF XChange Viewer
has offered many of these features for free for quite some time, so it's a bit frustrating to see everyone getting excited about Nitro when it's really just "joining the party" that others started.
That being said it's a more well-known name than PDF Xchange Viewer, so hopefully it will catch on. I think the UI might be a bit better, too.
I haven't tried Nitro yet, but did have a couple concerns I thought others might be interested to consider.
First, PDF Xchange Viewer can be used for commercial purposes for free, as far as I know. I don't know if Nitro is intended to remain free for that purpose, but hopefully so. The built-in collaboration features would tend to suggest the answer is yet.
Second, for those concerned about privacy, make note of this "feature" listed on their website:
"Product Improvement Program: gathers anonymous statistics about usage patterns and click sequences, to help us improve Nitro Reader’s tool functionality and user interface based on your live use of the product."