For me,I think root is needed for galaxy s4,I used my brother s4 for 2 days,there are some ui lag which my nexus 4 doesn't have,and the settings part are complicated to me,also the battery life is not as good as my rooted nexus 4(maybe cause I use custom kernel and ROM),but if galaxy s4 with CM10.1,I would say its a perfect phone,the volume,function,and everything is much better than my nexus 4,except smoothness

Haha ya,BTW s4 got one kind of feeling,its smaller but bigger compare to s3,I can't tell the screen size difference between my brother s4 and my nexus 4 in pie mode,BTW what's TW?