With all the features manufacturers have been putting into 4K sets, like curved screens and large speakers, it can be easy to forget that the heart of 4K is the picture. The Samsung U8550 series delivers a solid 4K experience without all the bells and whistles that would jack up the price.
The U8550 might not curve like the more higher-end U9000, but Reviewed.com says "trim bezels and a very narrow panel lend this television a modern air." The user interface is also attractive and easy to use, with LCD TV Buying Guide noting that it hits "the mark with ... user interface and intuitive navigation" and "Samsung really pays attention to the details," calling it "one of the best options for a good smart TV experience."
So the design looks good and so does the interface, but what about the picture itself? Reviewed.com notes it exhibits "healthy black levels and bright, vibrant white levels" as well as "impressive shadows and satisfying highlights, thanks to the TV's Smart LED local dimming." Home Theater Review did note "some minor brightness-uniformity issues," but Reviewed.com says "its uniformity is much better than standard edge-lit LED performance" and overall, the U8550 "is a testament to what the newest models are capable of."
The Samsung U8550 may not deliver as good a picture as the U9000 or the Panasonic AX800, but for a price that's about $1000 cheaper, it's still a solid option.