Yes I have and it didn't end up well. They are scam and only the first adopters benefit from it. Don't try it please.
Stay away from such things...I have had worst experience with such sites in early 2015 and at a time when bitcoin was just starting its big run from 250 usd level, this type of websites popped up in large numbers and swindled the money of people in the name of high return. There is a segment which is popularly known as HYIP(High Yield Investment Program) and these are mostly scam programs but people are so greedy that they used to get into the trap of such people.
These types of program and investment will pay you for the initial 2 or 3 weeks and after that they will suddenly disappear. So the best thing to do is that do not run after short cuts that will make you poor and your life will be worst than what you are now. Crypto ecosystem in itself is a better investment and here you are the sole owner of the crypto assets which you hold. So make a proper plan and set a larger time frame and in that time frame you can definitely make a lot of money if you have patience, because crypto will value higher at some point of time and crypto ecosystem in itself is a store of value.
Nope, I've never used any one and I don't think anyone should ever use them in the first place. For starters, I have a friend who invested alot of his money into one of these things and like all Ponzi schemes in the crypto world, he mad some profit at first and just because they called it "mining" he felt it was legit.
Soon after he started getting people in on it and started collecting money from them and investing it till one day the site just disappeared and so did all the money he invested.
It never ends well with these sites unless you're lucky enough to jump in and jump out before the site actually crashes or stops paying people, if not you're most certainly going to lose some money.
I hope this helps.
Off course not only retards put money in those type of scams.
If you fall for things like that investing is nothing for you at all.