Just to add my nickel here. I have that set and use it in 4.9 with no issues at all beyond needing to tweak them for each scene. Lights in Iray are very dependent on your render settings, (f-stop, shutter speed and whatnot). It's really a good idea though to read up on shutter speed, f-stop, film ISO and exposure value (found in Iray render settings under Tone Mapping) as these will affect your scene to a great degree. Lazy bugger that I am, I typically only adjust the luminance values up and down as necessary. Neon and monitor luminance especially can come out too bright. In my last render, I toned the neon values for Stonemasons Urban Futures 2 set down to 900, and some of the lit signage down to 300. It will all depend, so fiddle with smaller test renders first. Sickleyield has some really good journal articles on her deviantart page that covers a lot of Iray settings.