Copy/pasted from the thread about these same lights in the Visual/Body Modifications board:

Quote Originally Posted by RareGMFan View Post
There are only 2 brands making projector headlights. 99% of members have the version shown in this thread. The other ones aren't even worth mentioning due to the inferior quality of the...."projectors". As for these, from what I've read....

Pros
MUCH better light output vs. stock headlight housings.
Halos are a nice touch, but if you don't care for them, they don't have to be wired/turned on.

Cons
Cut-off's too low (adjusting them till the light output is high enough tends to leave a big gap between the headlights and body of the car).
Some have bouncing issues.
Some have leaking/condensation issues.
Using HID bulbs will void the warranty.

BTW, if you're planning to take this apart to do anything internal to them, I've read several times that the lenses are too brittle, and don't withstand baking to remove them.