I have a set and I am happy with the over-all quality. They didn't scratch the slide on the install or anything, so I guess I can't complain. I have read on a lot of other forums that PT sights generally only last 4-6 years before getting too dim. A lot of people prefer meprolights or trijicons for that reason, but I don't believe we M owners have a choice. Who else (except factory) makes Steyr night sights?
Overall, I would say they are worth the relatively low cost considering they do the install and they are gauranteed for life, so you can always just send them in down the line.