Real refinements cannot be restricted on UI or under the hood only. Average user doesn't give flying duck if there were gazillion improvements and features under the hood if learning curve to use them is too steep. Simplifying the UI eases the adoption of new (for average user) UI paradigm, even if some tricks have to be sacrificed because of it. Personally I like the new UI, it feels more polished, non-stuttering and consistent than the previous one, even if I had some reservations about it before the early adopter release. Just remembering the feature set of old Symbian phones... and how awkward it was to use at times.

Now, UI and Android support have been in the center of development because those are needed for the Tablet - Android apps ease the adoption by bridging the app-gap to other platforms and it needs to work out of the box. If it's as unstable and lacking as it were in the launch of the phone, it will be an utter, complete disaster. So, it's understandable that they have been given priority at this stage of development. Unfortunately it has been the trade off using different type of SoC in Tablet.