I don't think I'll be getting the Galaxy S4. I currently have a Galaxy S3 and think it is a great device but my initial plan when switching to Android was to go with the Nexus line for both my tablet and smartphone. I didn't get the Galaxy Nexus because it was very much outdated at the time I bought the S3 but with Google I/O coming I think we can expect either a new smartphone (the rumoured "X Phone"), a spec bump for the Nexus 4 or both and as such it would be an opportunity for me to switch to a Google/Nexus smartphone with the same benefits of my Nexus 7.
I am also not too hot for Samsung as a company at the moment, they have been rubbing me the wrong way as of late, their blatant rip off of Apple's Passbook being the latest offence. It is also virtually certain that since they are such a big OEM they will end up pushing their own Tizen OS with their own ecosystem including all the Samsung apps/services (S-Voice, Samsung Wallet, their store for video, music and magazines, cloud storage, email, browser, etc). I am personally not interested in any of that or in Samsung seeking to replace services and functionality that Google includes in Android by default. I trust Google (and Apple), I don't trust Samsung.