It's alright to use to gain a few extra bucks if a person has some free time. A person can get points in a number of ways. The more common ways are surveys, watching videos, and shopping. Need 500 points at a minimum to get a reward which is usually a 5 dollar gift card. It takes 2500 points to get cash ($25) through PayPal. It usually takes about a week to get a gift card or money from Swagbucks after you claim your reward.
However it can be difficult to accumulate points as if you don't qualify for a survey you get one point. And you can only gain a maximum of 5 points daily from surveys that you don't qualify for. Can be very time consuming. Sometimes a person qualifies for a number of surveys in a short period of time. It depends on who is conducting surveys, and if they are a match for you. Most surveys are 75 points. Some have point values less than 75 points and others have higher point values.
Usually have to watch 20 videos to get 3 points most of the time. It's a mighty slow way to get points. A person who has a lot of free time on their hands like a retiree, senior, or disabled person might be happy with that though.
I haven't tried to get points via shopping. I haven't come across any products thus far that I need where I would benefit from that.
I haven't come across any "gotchas," questionable practices, scams, or anything else of that sort. So, I can't say that it's harmful in any way. For a person who has free time it's a way to get some gift cards and/or make a little cash. A person won't get wealthy from this.