I just bought a G17L from Glockmeister and had them install the TFO sights on the gun before shipping. I received the gun two days ago and promptly took it to the range and put about 500 rounds through it. It's a private, indoor range where I usually have the place to myself. I was able to try the sights under various lighting conditions, including virtually no light. I was VERY impressed by the TFO sights. Very quick target acquisition and although adjustable, Glockmeister seems to have done a perfect job installing them. I paid an additional $99 for the sights, installed, when I bought the gun. I'd highly recommend them. I chose the green/green combo due my use equally outdoors and in. I'm sure the green/amber combo would work well, too. If you're looking at a sight upgrade, I don't think you can go wrong with these Trijicon sights. My two cents.
I have them on my G19 and love them! The more light you have the better, and when it is completely dark they glow brightly from the tritium. I have a bunch of friends that also have/love them. It is amazing when the sun is going down with the ground covered with snow. I have a picture if I can figure out how to post it. Bottom line...get them you won't be dissapointed.