I have purchase a few to try but have not put them in yet, still determining where I want to put them, likely going to start on inserts on SWEP1. I know I would not like them as GI lights. If I found a good soft 'amber' white lamp I may consider it. By their nature, LED's are 'blue' white.
Yes LED's, due to their lightwaves can cause headaches, especially after long exposure. Despite appearances they do not give off a direct light, but rather dispursted, uneven fields of light with lots of grey areas, that even the slightest movement of ones head causes the light to look different, or at least it registers different to the eye and mind, even if you don't conciously notice the difference.
As for the dimmable nature of LED's, it is something that has yet to be mastered, even for high dollar LED fixtures used in the entertainment industry. I work with all sorts of LED fixtures and have only come across one fixture that has any respectable low-end dimming curve, most others are on/off no matter if the voltage input is 0% or 15%, but dim somewhat smoothly between 15%-100% voltage. This is considered one of the weakest flaws of using LED's as a main light source in entertainment.