It is good to read of some of the gains, which I am sure are helpful to a number of users.
That said, there are a number of organizational and formatting details missing which were present in '09, quick access to individual sheets in a side bar, being able to see a print view of your page to name a few. It is still so far off what I can use day to day that I have had to delete the current Numbers/Pages suite from my drive until some of this comes back in some form. Too bad.
This thread is intended to show what has been gained.
What has been lost in Numbers 3 is here (with corrections where Apple has already reinstated some lost features in the Numbers 3.0.1 update):
Many features have been lost in Numbers 3. You can send feedback to Apple with Menu > Numbers > Provide Numbers Feedback.
Features that Apple has promised to reinstate:
Hints on workarounds here: