Zen,
Just my .02, but if you're talking house gun, not carry gun, I think a tactical light is MORE important that the nite sites, and I prefer an attached light. But I do like having them (both) on my USP 45. I felt the sites were important enough that I put them on my wife's Kahr MK9. Another bonus...in pitch dark, they're like little runway lights when you're reaching for your pistol.
As far as being seen by the BG, I've gone into the bathroom, shut the door, turned off the lights, and tried different angles to see if I could spot myself in the mirror. Only the slightest hint of a glow from a couple of angles, the WORST angles though, I might add. (to the side-rear).
I think meprolite makes the factory HK sites, and those are the ones I have. They work great for me. Whoever they are, they're the same brand I bought for the little wife too.
In sum, I love my nite sites, but I would give em up in a second if it was them or my UTL.