Engadget posted a review of the Galaxy S3, and while they think the phone is excellent, they're not sure if the S3 is the best Android phone on the market, with the main competitor being the HTC One X. They love the 1280x720 4.8" Super AMOLED HD display, and say that there are real visual improvements over the Galaxy Nexus. The colors aren't over-saturated and there's no unnatural blue-ish tint.
Regarding the controversial PenTile technology, Engadget says that it isn't so visible because the screen is large and you tend to hold it from a little bit further than in smaller phones. But it still makes text a bit fuzzy, and so if you like reading on your book, maybe it's better to choose a non-Pentile phone (I personally think it's better to use a dedicated e-paper e-reader if you actually want to read).
The S3 pre-order numbers are very strong, and it seems that Samsung has another winner at their hands. But when the S2 was released, it was clearly the best Android phone around, and this time it seems that there is stronger competition. Amazon are now offering the Galaxy S3 unlocked for $799.99, and it will ship on June 1st.