It definitely made them friendlier, at least during the time they were in there and for a week or so after I put them back in the big brooder.
I'm thinking if you want them to be pets, the best way would be to have few chickens, get them VERY used to seeing you and interacting when they are babies, and give LOTS of treats as they grow up.
Even the ones that were skittish as chicks come for treats now, though, and now that they are starting to squat, they are easy to pick up most of the time. I think treats is the biggest factor.
Early personality doesn't seem to have an absolute prediction on the friendliness of grown chickens. My barred rocks were always the last ones I caught for transfer, because they ran away, screamed the loudest, and struggled the most when picked up. Now they are pretty friendly, and one of them will follow us around and around our about-an-acre yard without the benefit of treats. She just seems to like the company. She "talks" to us all the time too.
But the glass brooder helped in the beginning. If I'd kept just a few in there, I think it would have made a difference. I kept the little Jap Bantam in there the longest, and he stayed friendly through his whole extended-brooder period. The first night I built the coop, I kept him in the house by himself in their shipping box (cuz he was my favorite), and he never fussed about being alone or tried to escape. He would just stay where I put him.
He's a little roo tho, and now he tries to stay out of my way. He does NOT want to be picked up, LOL, tho I hear some roos are friendly that way.
Good luck to you,
trish