Microsoft went through this issue with the change in the Office product suite from the old style button bar-centric view to the new tabbed format. They took this radical step because somewhere around 95% of the new feature requests they received were for features that were already in the software. The issue was not lack of capability, but poor feature discoverability. Clearly, something had to change.
 
Boatloads of people hated the new tabs and called the new design all sorts of bad names. However, testing showed that people found and used far more of the existing feature set than in the previous UI. Casual users hated it, but the people that used the software day in and day out were much more productive with the new layout.
 
It's always a very tough decision to pull the rug out from under your users, but sometimes it just has to be done.