The iPad Air 2 has the same 9.7-inch display as previous generations – with a resolution of 2048*1536. This gives a pixel density of 264 PPI. While on a tablet this is perfectly acceptable, compared to the iPad Mini 2 (which has the same resolution but across a smaller screen) this display is noticeably less crisp. Still, that is the price to pay for the larger screen.
Improvements have been made on the display, though, in other areas. For one, there is an improved contrast ratio – going from 968:1 to the current nominal figure of 1048:1. It's not much, but blacks are deep and colours are vivid.
The last 5 generations of iPads and iPad minis have all had IPS displays, and so it is no surprise the iPad Air 2 uses the same in-plane switching technology. Viewing angles are great, and is something the iPad has done consistently well since its inception.
Also of note is the anti-reflective coating Apple include with the iPad Air 2. The first such coating on any iPad, it does make a difference. Compared with an iPad Mini 3, for instance, reflections are much more muted and less prominent – which makes using the tablet outdoors much easier.
All in all, the different new improvements mean the iPad Air 2 has a very impressive display.