i guess it really boils down to individuals...
for me... i'm used to SWIPE. no swype, its not really a touchscreen keyboard la... coz we have so many swipe and gestures but keyboard still need to tap like the old physical keyboard?!? accuracy-wise, swipe is accurate.
retina display... how to define it? based on PPI? if so... S4 will have about 441 pixels per inch, assuming rumours of fullHD on 4.99" screen is true.
i never liked titanium or any 'metal' body. drop it a bit and you get a permanent dent. ouch...
camera... ok la... but you've shown ma... Note 2 also can take nice photos.

so, i'd think the same with S4.
spen tech without spen is not possible coz spen uses WACOM tech which employs some sort of magnetic thingy. so unless you have new accessories like maybe wear a finger glove... else i doubt out finger will have magnetic power strong enuff to do the air view thingy... well, unless you're Magneto... heh heh...
i actually wish Samsung would just remove those physical buttons... but what to do... still need that since its the one thing iPhone users are so familiar with -- yes, i believe samsung is targetting iPhone users.
for the camera part sure better than note 2 and s3, if not they no point release new phone right ?
even not better than note 2 or s3, I think at least got new features, but I don't think got what new features already