No dimming.
And warmup is about 5 minutes.
And yes, they need a special ballast.

They are not a general replacement as people are trying to get you to do. I'm simply pointing out there are non-standard light sources that most people don't deal with, yet the spectrucm they provide is far better than what most people live under.

In this house, the guy went all out on a variety of lights, so I got choices.