They’re needlessly complicated, expensive to repair, and they provide about half of the light of a halogen headlight. I’ve never driven a vehicle with HIDs and had a thought other than “these headlights are shit”, and I’ve never had a car with HIDs drive towards me and had a thought other than “those are like a laser beam straight to my cornea”.
I’m talking OEM setups here, too- not the Chinesium eBay plug-n-spray conversions. Those are a whole different set of peeves.