God... i hate it if people always complain about useless reasons!
Instead of being sad that we have been losing nearly all customizability functions we users should be happy that we finally get a stock UI which is ALREADY optimized so that it is not necessary anymore to mess around until the perfect workflow is created.
And not to forget, customization features are still bloat which slow down a program. People who want to have such an experience can customize over add-ons, which is the only valid way to do it.
Seriously, how often do you customize your browser? every day? every week? Fact is you do it most of the time ONCE and then you ignore the features for very long time. So having such features in add-on form is the more preferred, more better way to handle tasks like that.
Opera has just decided to bring us a competitive engine with the most possible workflow optimizations possible! And for that we should not be whining of what we have lost, we should embrace what we instead win!