Most affordable 4K monitors are based on TN technology, but not the latest duo from Dell. The 23.8" P2415Q and 27" P2715Q both feature IPS panels. They're still priced like TN displays, though. The 24-incher is selling for $599.99, while its 27" sibling is listed at $699.99.
Apart from their screen sizes, the two displays are nearly identical. Dell claims that both are factory-calibrated to deliver "nearly perfect color accuracy," with 99% sRGB coverage and a delta-E of less than three. The displays produce 1.07 billion distinct shades, but they probably don't use true 10-bit tech. My money's on 8-bit panels augmented by dithering.
Unlike Dell's initial foray, which was limited to 30Hz at full resolution, these new models can push 3840x2160 images at 60Hz. Both have 178° viewing angles, 1000:1 contrast ratios, and 6-ms "fast" response times. The P2415Q has a 300-cd/m² brightness rating and an 8-ms "typical" response time, while the P2715Q is rated for 350 cd/m² and 9 ms.
The stands are adjustable every which way, and they can be swapped for VESA-compatible mounts. Connectivity includes a four-to-one USB 3.0 hub, an MHL-compatible HDMI port, a DisplayPort input, and a DP output that supports daisy-chaining a second screen.
Given everything, these look like very nice monitors for the money. The only detriments seem to be the slower response times, which aren't uncommon for IPS displays, and the lack of variable refresh support, which is still a rarity. Thanks to TFT Central for the tip.