when you’re playing for the long run it is better to be nice — you’ll make up any short-term losses with long-term gains.
It also depend on the population distribution. If everybody else is mean, being nice in long run still lose. So the optimal strategies in different culture are obviously different.
I think TIT FOR TAT is good because: 1. it give a gesture for cooperation at first 2. but respond immediately if the response is hostile.
There were some variations of TIT FOR TAT, like being nice for several rounds, then revenge later. Those variations didn't work well.
The random strategy(being nice or mean randomly) also doesn't work because it's difficult for others to predict your behavior.
The experiment was designed for long term survival, so it doesn't apply to these cases:
Being nice for all the time, then use the reputation to scoop the biggest gain in the last step.
So the experiment is very interesting and revealed a lot of points, but the simple takeaway of "being nice is good for long term" is just too limited.