I'm the first one to jump on the Anti-PenTile bandwagon, but it's only really a problem on my S3 when I look too closely at it, and while I'll be reserving judgement for when I see the S4 in person, I don't think it'll be an issue on a 1080x1920 display.
As for colour reproduction, I like the AMOLED saturation. It makes colours pop and feel far more vibrant. When I look at a One X or an iPhone 5, the colours look too washed out to me. Also, Samsung handsets have Screen Mode options, in which you can change the display calibration to be more like an LCD.
Thanks. This is at least an opinion worth debating (which the OP failed to provide).
We have pretty much all mobiles in use in our company (as we have a, more or less, free BYOD program - we do not allow Windows Phone yet, as the OS does not support NTP yet - and reliable time syncing is mandatory in our business - and because InternetExploder can't render our Intranet pages properly, but we do allow iOS, Android and BB7+), and I did a lot of testing using all of them.
As I said before, Pen Tile displays are OK for irregular patterns (pretty much everything except for text and detailed line graphics). But the S3 does definitely not render text any way close to the iPhone models with the "Retina" displays. The text is jaggy (not only when looking from a less than usual distance, but always); not terrible by any means, but not distinctively better than on a non-"Retina" display several years ago. Of course, this also depends on the actual font. While it is not that noticeable with massive fonts (like most fatter sans serif fonts), it is fairly obvious with more fragile fonts (like normal weight Times). People mainly using a phone for photos, videos and games will likely not notice it at all. People reading a lot of blogs, books and magazines will see a clear difference. I do not mind as long as people are happy with what they have, but stating it is the same is not quite right.
The same goes for color accuracy. If somebody likes extreme colors and red faces in movies, it is not up to me to call them wrong. Still, there is only one "correct". I often use my iPhone and iPad to check and rate pictures from my DSLR before I send them to my company. I have tested several OLED screens, and they were all completely useless for this task. I am not saying everybody needs this accuracy, just that there is a clear and obvious difference. The "Screen Mode" options on Samsung's devices mainly do two things: de-saturate the screen or change the color balance / temperature. This does indeed change the impression of the image (and eventually makes it more pleasing to look at, or closer to the expectation), it does not make it more accurate. People not needing accuracy might be completely fine with that, no objection at all, but saying it is anywhere close to accuracy is just wrong.
(Disclaimer: I am not at all stating here that any iPhone or iPad would be suitable for color critical tasks, like proofing or color correction... they are not. But they give me a pretty close impression of what somebody else will see on a decent, calibrated screen. Not exact. But close. OLED can't do that. Not because they do not want to, it is a technical limitation of the panel technology.)