First of all, halos look absolutely brilliant inside the M headlamp fixture where they are surrounded by the highly polished chrome. That car in the video with the square headlight? Not so much.
I wanted some kind of DRL for my M and was seriously considering getting halos for both the high beam and main headlamp surrounds. After looking at many ideas, it seemed the halos, while great for effect, didn't really work all that well as DRLs. They can't be seen very well from a distance and not at all when sunlight hits the housing directly.
Also, years ago when BMW started using them in their models, it was fresh, unique, and anytime you saw halos, your first thought was BMW. Now you can find halos of some sort on everything from cheap pushers to Rolls Royce. Not a unique idea by far, but still staggering if used in the right housing like our M's.
Also, to add halos on the M, you have to pretty much remove the front of the car to get to them, then break the seal to open the housing and install them, then seal them back up again, hoping you didn't leave a space for moisture to build up and fog the lens. Even the best halos would look crap inside a headlight assmebly with water vapor inside of it. Then ... what happens if one halo goes out? You have to repaeat that whole project all over again.
So ... I decided on a high quality LED DRL that attached to the car. Mine are properly aligned and angled to NOT glare at pedestrians or shine directly into the eyes of oncoming drivers, but they are still highly visible to oncoming traffice from a longer distance than halos. I still love the way halos dress up the M. I decided in the end to have actual DRLs instead of a halo. If one DRL goes out, It's easy to replace it in minutes without dismantling the car and hours of labour.
If you do this project I would suggest buying the halos from a reputable manufacturer with bright halos and find a size that best fits around each housing. Here is the sight I was planning on using if I went in that direction. They seemed to have the highest quality and even if the halo is slightly too long, you can just let the reamining few cm of the halo run inside the housing at the bottom where it won't be noticed.
http://www.bimmian.com/PHO/
.
Please post pics if you do this project as I'm sure many of the members would love to have a DYI with pics for this!