I have been using them for about 3 years now with no problems. Have not had any fixture go bad yet. However I did have a couple of fixtures out of the box with problems...bad screw tap, cracked lens ect but all it took was one call and a new one was at my office in 3 days. Customer service is awesome. The bullets and MR-16 well lights are great with the exception of the "Fat Boy" seems a bit cheap. I did however use it with their 10W LED Bulb and it has been working fine for 2 years. The integrated LED bullets (Infinity) have a really nice color temp and are impressive fixtures.
If I had to criticize anything it would be their bulbs. The standard MR-16's are too cool, the bi-pins burn out too fast and the LED Bi-Pins are too cool. MR-16 LED are very good. I had 2 out of about 30 burn out after a year but they were replaced by them at no charge. The 2 were down lights on the same tree..not sure why they burned out but possibly too much grease.
The transformers are UL listed, not sure about the fixtures.