Light Flow is fantastic and one of the best selling points of Android customization through third-party apps in my opinion. I tell everyone I can about it and show it off often.
I do honestly have concerns though that it does not work 100% of the time. There are times when I get a text and get my alert tone but no notification light. This does not happen frequently enough for me to look for alternatives, but it is noticeable.
One thing that may be an issue is that when I leave Messaging open (the stock messaging app) and the screen goes to standby, I will get the alert no light incident.
Overall, love it!