I love some of the features that Touchwiz provides, but the UI doesn't have to look like that to accomplish the same feature set. Google has provided an outstanding UI and application design structure, and Samsung continues to ignore it with their 2011 appearance. It's frustrating.
The need for physical buttons also went away with ICS 4.0 in 2011, yet we're still seeing them over and over. I haven't owned a Samsung product since the GNex, mostly because I play with them in the stores and that button feels cheap and unreliable. That may just be the display models, but I can't understand why Samsung is 6 months ahead of other OEMs in features, but 2 years behind in design of UI and hardware. Taking some queues from Google and HTC, etc. would be a great benefit to them and consumers.
The main benefit of the S4 to me is that it sets a new bar for the other really great phones of 2nd and 3rd quarter to surpass; just like the S3 did last year. This phone is awesome, and I hope it sells well; but their refusal to recognize that 2 years have passed since ICS is incentive enough for many to wait for the X Phone, Nexus 5, etc, which are both expected to be leaps and bounds ahead of the Q1 releases by HTC, LG and Samsung.