Scene 01: Basic scene illuminated by HDR environment, self-illuminated material (spiral geometry), and a photometric light (sphere). This scene isn’t really any different from how I would configure a mental ray scene, other than it’s using iray.
Scene 02: This scene is using a daylight system. This does work a bit differently than it does with mental ray. You’ll notice the mrSun/mrSky lights are actually disabled, yet it’s still illuminated. That’s because it’s using the environment (mrPhysical sky) instead of the lights. The daylight lights (mrSun/mrSky) are still useful for positioning the sunlight angle though. So if you move them, the light changes as you’d expect.
Adjustments are a bit different here though. I drag the mrPhysical sky from the environment to the material editor and adjust the Disk Intensity and Glow intensity to tune the sunlight brightness/hardness. And of course the non-physical tuning options of the physical sky or mrsky will adjust the blue/red tint of the light/sky.
Hope this help get people started with iray while waiting for some detailed/scene specific/step-by-step tutorials to start appearing.